DHPN-1007
`Dell Inc. vs. Electronics and Telecommunications, IPR2013-00635
`Page 1 of 43
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`

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`FOR THE PURPOSES OF INFORMATION ONLY
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`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.
`
`Albania
`Armenia
`Austria
`Australia
`Azerbaijan
`Bosnia and Herzegovina
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Central African Republic
`Congo
`Switzerland
`Cote d‘Ivoire
`Cameroon
`China
`Cuba
`Czech Republic
`Germany
`Denmark
`Estonia
`
`ES
`FI
`FR
`GA
`GB
`GE
`GH
`GN
`GR
`HU
`IE
`IL
`IS
`IT
`JP
`KE
`KG
`KP
`
`KR
`KZ
`LC
`LI
`LK
`LR
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Ireland
`Israel
`Iceland
`Italy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People’s
`Republic of Korea
`Republic of Korea
`Kazakstan
`Saint Lucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`LS
`LT
`LU
`LV
`MC
`MD
`MG
`MK
`
`ML
`MN
`MR
`MW
`MX
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`
`Lesotho
`Lithuania
`Luxembourg
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`The former Yugoslav
`Republic of Macedonia
`Mali
`Mongolia
`Mauritania
`Malawi
`Mexico
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`Sweden
`Singapore
`
`SI
`SK
`SN
`SZ
`TD
`TG
`
`TM
`TR
`TT
`UA
`UG
`US
`UZ
`VN
`YU
`ZW
`
`Slovenia
`Slovakia
`Senegal
`Swaziland
`Chad
`Togo
`Tajikistan
`Turkmenistan
`Turkey
`Trinidad and Tobago
`Ukraine
`Uganda
`United States of America
`Uzbekistan
`Viet Nam
`Yugoslavia
`Zimbabwe
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`DHPN-1007 I Page 2 of 43
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`DHPN-1007 / Page 2 of 43
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`

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`WO 99/38067
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`PCT/US99/01282
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`AN APPARATUS AND METHOD FOR AUTOMATIC CONFIGURATION
`
`OF A RAID CONTROLLER
`
`.EI..:|I.
`
`The present invention relates generally to peripheral controllers. More
`
`particularly, the invention relates to the automatic configuration of Redundant Array
`
`of Independent Disks (RAID) controllers.
`
`
`
`RAID is a technology used to improve the I/O performance and reliability of
`
`mass storage devices. Data is stored across multiple disks in order to provide
`
`immediate access to the data despite one or more disk failures. The RAID
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`technology is typically associated with a taxomony of techniques, where each
`
`technique is referred to by a RAID level. There are six basic RAID levels, each
`
`having its own benefits and disadvantages. RAID level 2 uses non-standard disks
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`and as such is not commercially feasible.
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`RAID level 0 employs “striping" where the data is broken into a number of
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`stripes which are stored across the disks in the array. This technique provides higher
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`performance in accessing the data but provides no redundancy which is needed for
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`disk failures.
`
`RAID level 1 employs “mirroring” where each unit of data is duplicated or
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`“mirrored” onto another disk drive. Mirroring requires two or more disk drives. For
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`read operations, this technique is advantageous since the read operations can be
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`performed in parallel. A drawback with mirroring is that it achieves a storage
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`efficiency of only 50%.
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`WO 99/38067
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`2
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`In RAID level 3, a data block is partitioned into stripes which are striped
`
`across a set of drives. A separate parity drive is used to store the parity bytes
`
`associated with the data block. The parity is used for data redundancy. Data can be
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`regenerated when there is a single drive failure from the data on the remaining drives
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`and the parity drive. This type of data management is advantageous since it requires
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`less space than mirroring and only a single parity drive. In addition, the data is
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`accessed in parallel from each drive which is beneficial for large file transfers.
`
`However, performance is poor for high I/O transaction applications since it requires
`
`access to each drive in the array.
`
`In RAID level 4, an entire data block is written to a disk drive. Parity for
`
`each data block is stored on a single parity drive. Since each disk is accessed
`
`independently, this technique is beneficial for high I/O transaction applications. A
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`drawback with this technique is the single parity disk which becomes a bottleneck
`
`since the single parity drive needs to be accessed for each write operation. This is
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`especially burdensome when there are a number of small I/O operations scattered
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`randomly across the disks in the array.
`
`In RAID level 5, a data block is partitioned into stripes which are striped
`
`across the disk drives. Parity for the data blocks is distributed across the drives
`
`thereby reducing the bottleneck inherent to level 4 which stores the parity on a single
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`disk drive. This technique offers fast throughput for small data files but performs
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`poorly for large data files.
`
`A typical data storage system can contain a number of disk storage devices
`
`that can be arranged in accordance with one or more RAID levels. A RAID
`
`controller is a device that is used to manage one or more arrays of RAID disk drives.
`
`The RAID controller is responsible for configuring the physical drives in a data
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`storage system into logical drives where each logical drive is managed in accordance
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`with one of the RAID levels.
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`WO 99/38067
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`PCT/US99/01282
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`3
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`RAID controllers are complex and difficult to configure. This is due in part
`
`to the numerous possible configurations that can be achieved, the knowledge
`
`required by a user to configure such a system, and the time consumed by a user in
`
`configuring the controller. In one such RAID controller configuration procedure, an
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`automatic configuration feature is provided that attempts to alleviate the user’s input
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`by automatically configuring a number of devices at system initialization. However,
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`this automatic configuration feature is very limited and only operates where all the
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`physical disk drives are of the same physical size and where there are between 3 to 8
`
`disk drives. In this case, the automatic configuration feature configures the disk
`
`drives as a single drive group defined as a RAID level 5 system drive with no spare
`
`drives. This configuration is limited providing no other alternate configurations.
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`Accordingly, there exists a need for an automatic RAID controller
`
`configuration mechanism that can accommodate various types of RAID level
`
`configurations and for disk drives having various physical dimensions.
`
`&
`
`The present invention pertains to an apparatus and method for automatically
`
`configuring disk drives connected to a RAID controller. The automatic
`
`configuration mechanism is able to generate a full configuration of the disk drives
`
`connected to a RAID controller both at system initialization or bootup and at
`
`runtime. The mechanism uses a robust criteria to configure the disk drives which
`
`allows the drives to be configured in accordance with one or more RAID levels and
`
`with various default settings that affect the operation of the disk array.
`
`In a preferred embodiment, the automatic configuration mechanism includes
`
`a startup configuration procedure that provides the automatic configuration
`
`capability at system initialization and a runtime configuration procedure that
`
`automatically configures disk drives connected to the RAID controller at runtime.
`
`The startup configuration procedure generates a full configuration of the disk drives.
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`The configuration specifies the logical drives that are formed and the associated
`
`operational characteristics for each logical drive which includes the RAID level, the
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`WO 99/38067
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`4
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`capacity, as well as other information. The startup configuration procedure can
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`accommodate previously existing configurations and partial configurations. In
`
`addition, the startup configuration procedure can configure unconfigured drives in
`
`accordance with a criteria that considers the existing configuration of the disk drives
`
`and which is able to select an appropriate RAID level suitable for optimizing the
`
`overall computer system’s performance.
`
`The runtime configuration procedure is used to configure disk drives
`
`connected to the RAID controller while the system is operational. The inserted disk
`
`drives can be part of an existing configuration or can be unconfigured. The runtime
`
`configuration procedure can incorporate the configured drives into the current
`
`configuration as well as configure the unconfigured drives. The unconfigured drives
`
`are configured in accordance with a criteria that uses the inserted disk drives to
`
`replace dead or failed drives, that adds the inserted disk drives to certain logical
`
`drives that can support the additional capacity at the defined RAID level, and that
`
`forms additional logical drives as needed.
`
`The automatic configuration mechanism is advantageous since it eliminates
`
`user interaction required to configure disk drives connected to a RAID controller. In
`
`addition, the mechanism allows disk drives to be configured into one or more RAID
`
`levels in a manner that considers the current state of the disk drives and that
`
`optimizes the overall system performance. The mechanism is flexible performing
`
`the automatic configuration both at runtime and at system initialization.
`
`PEI
`
`.. “I.
`
`For a better understanding of the nature and objects of the invention,
`
`reference should be made to the following detailed description taken in conjunction
`
`with the accompanying drawings, in which:
`
`FIGS. 1A-1B illustrates a computer system in accordance with the preferred
`
`30
`
`embodiments of the present invention.
`
`FIG. 2 illustrates a RAID controller in accordance with a preferred
`
`embodiment of the present invention.
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`5
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`FIG. 3 is a flow chart illustrating the steps used to manually configure a set
`
`of disk drives.
`
`FIGS. 4 - 5 illustrate the process of forming and ordering drive groups from
`
`physical drives in a preferred embodiment of the present invention.
`
`FIG. 6 illustrates an exemplary assignment of RAID levels to a set of logical
`
`drives in accordance with a preferred embodiment of the present invention.
`
`FIG. 7 is a flow chart illustrating the steps used in the startup configuration
`
`procedure in a preferred embodiment of the present invention.
`
`FIG. 8 is a flow chart illustrating the steps used to scan the physical devices
`
`connected to the RAID controller in a preferred embodiment of the present
`
`invention.
`
`FIG. 9 is a flow chart illustrating the logical drive order rules of a preferred
`
`embodiment of the present invention.
`
`FIG. 10 is a flow chart illustrating the steps used in the runtime configuration
`
`procedure in a preferred embodiment of the present invention.
`
`FIG. 11 is a flow chart illustrating the steps used to add capacity in
`
`accordance with a preferred embodiment of the present invention.
`
`Like reference numerals refer to corresponding parts throughout the several
`
`views of the drawings.
`
`I
`
`.1
`
`1 I
`
`.
`
`.
`
`E 1
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`I
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`.
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`Fig. 1A illustrates a host system 100 utilizing the RAID controller 102 in a
`
`first preferred embodiment of the present invention. There is shown the RAID
`
`controller 102 connected to a host peripheral bus 104 and one or more Small
`
`Computer System Interface (SCSI) channels 106A-106N.
`
`In a preferred
`
`embodiment, the RAID controller 102 can be any of the Mylexm RAID controllers,
`
`such as but not limited to the DAC960 series of RAID controllers. The operation of
`
`SCSI channels is well known in the art and a more detailed description can be found
`
`in Ancot Corporation, Basics of SCSI, third edition, (1992-1996), which is hereby
`
`incorporated by reference.
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`6
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`The host peripheral bus 104 is connected to a host central processing unit
`
`(CPU) and memory 108. The host peripheral bus 104 can be any type of peripheral
`
`bus including but not limited the Peripheral Component Interconnect (PCI) bus,
`
`Industry Standard Architecture (ISA) bus, Extended Industry Standard Architecture
`
`(EISA) bus, Micro Channel Architecture, and the like. The host CPU and memory
`
`108 includes an operating system (not shown) that interacts with the RAID
`
`controller 102.
`
`Each SCSI channel 106 contains one or more peripheral devices 110A-1l0Z
`
`such as but not limited to disk drives, tape drives, various types of optical disk
`
`drives, printers, scanners, processors, communication devices, medium changers,
`
`and the like. A SCSI charmel 106A can be used to access peripheral devices located
`
`within the host system 100 or a SCSI channel 106N can be used to access peripheral
`
`devices external to the host system 100.
`
`Fig. 1B illustrates a computer system in accordance with a second preferred
`
`embodiment of the present invention. In this embodiment, the RAID controller 102
`
`is external to the host system 100. The RAID controller 102 is connected to the host
`
`system 100 through a SCSI channel 106A and is connected to one or more
`
`peripheral devices through one or more SCSI channels 106B-106N. The RAID
`
`controller 102 and the SCSI channels 106 are similar to what was described above
`
`with respect to Fig. 1A.
`
`Fig. 2 illustrates the components of the RAID controller 102. There is shown
`
`a CPU 112 connected to the host peripheral bus 104. The CPU 112 is also
`
`connected to a secondary peripheral bus 114 coupled to one or more SCSI I/O
`
`processors 116A-116N. A SCSI I/O processor 116 can be coupled to a SCSI
`
`channel 106A and acts as an interface between the secondary peripheral bus 114 and
`
`the SCSI channel 106. The CPU 112 is also coupled to a local bus 118 connected to
`
`a first memory device (memory,) 120, a second memory device (memoryz) 122, and
`
`a coprocessor 124. The coprocessor 124 is coupled to an on—board cache memory
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`126 which is under the control of the coprocessor 124. The coprocessor 124 and
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`7
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`cache memory 126 is used to retrieve data read to and written from the peripheral
`
`devices 110 as well as perform error correction code (ECC) encoding and decoding
`
`on data that is read to and from the peripheral devices 110. The cache memory 126
`
`can employ either a write-through or write-back caching strategy.
`
`In a preferred embodiment, the CPU 112 is a 32-bit Intel i960 RISC
`
`microprocessor, the first memory device 120 is a flash erasable/prograrnrnable read
`
`only memory (EPROM), the second memory device 122 is a non—volati1e random
`
`access memory (NVRAM), the host peripheral bus 104 is a primary PCI bus, and the
`
`second peripheral bus 114 is a secondary PCI bus. In the first memory device 120,
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`there can be stored a startup configuration procedure 128 and a runtime
`
`configuration procedure 130. The startup configuration procedure 128 is used to
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`automatically configure the disk drives at system initialization or bootup which
`
`occurs before the operating system is installed. The runtime configuration procedure
`
`128 is used to configure the disk drives while the operating system is operational.
`
`In the second memory device 122, there can be stored a configuration file 132
`
`containing the current configuration of the RAID disk drives.
`
`In addition, each physical disk drive associated with the RAID controller 102
`
`includes a configuration file 134 that includes data indicating the configuration of
`
`the drive.
`
`In an alternate embodiment, the second memory device 122 on the controller
`
`holds only configuration labels which identify the configuration files 134 on the
`
`physical disk drives, rather than holding the entire configuration information.
`
`The foregoing description has described the computer system utilizing the
`
`technology of the present invention. It should be noted that the present invention is
`
`not constrained to the configuration described above and that other configurations
`
`can be utilized. Attention now turns to a brief overview of the terminology that will
`
`be used to describe a preferred embodiment of the present invention. This
`
`terminology is explained in the context of the manual configuration procedure.
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`WO 99/38067
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`PCT/US99/01282
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`8
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`The manual configuration procedures are used to create logical disk drives
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`from an array of physical disk drives. Typically the configuration process is a
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`manual procedure that is initiated by a user. Fig. 3 illustrates the steps used in the
`
`manual configuration process. First, a user identifies one or more drive groups (step
`
`172), orders the drive groups (step 174), and creates and configures one or more
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`logical drives in each drive group with a RAID level as well as other parameter
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`settings (step 176). The configuration information is stored in each physical drive
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`and in the RAID controller (step 178). The logical drives are then initialized (step
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`180) and the configuration is presented by the RAID controller 102 to the host
`
`operating system (step 182). These steps will be described in more detail below.
`
`Fig. 4 illustrates a number of physical disk drives arranged in one or more
`
`drive groups 140, 142, 144 (step 172). The physical disk drives are connected to one
`
`of the SCSI channels 106. The physical disk drives can be arranged into one or
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`more drive groups 140, 142, 144. A drive group 140, 142, 144 is used to create
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`logical drives having a defined capacity, a RAID level, as well as other device
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`settings. The capacity is based on the aggregate of the capacities of each of the disk
`
`drives in the drive group and depends on the RAID level. In a preferred
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`embodiment, the RAID controller 102 can support up to eight drive groups. A drive
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`group can include one to eight physical drives. Drives that are not included in any
`
`drive group are considered standby or hot spare drives. The standby drive is a
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`redundant disk drive that is used when a disk drive fails.
`
`As shown in Fig. 4, the disk drives are configured into three drive groups
`
`referred to as drive group A 140, drive group B 142, and drive group C 144 with one
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`standby drive 146. Drive group A 140 contains three disk drives located on SCSI
`
`charmel 106A, drive group B 142 includes three disk drives located on SCSI channel
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`106B, and drive group C 144 includes two disk drives situated on SCSI channel
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`106A and one disk drive situated on SCSI channel 106B. Disk drive 146 is
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`30
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`considered the hot spare drive.
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`9
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`After all the disk groups have been identified, the drive groups are ordered
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`(step 174). The drive groups are ordered with a sequential numeric ordering from 1
`
`to n, where n is the highest order number. The ordering is used for certain operating
`
`system purposes and in particular to designate a primary logical drive that can serve
`
`as a boot drive. A boot drive is used to “boot-up” the physical drives in a
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`configuration which is described in more detail below.
`
`Next, logical drives in each drive group are created and configured (step
`
`176). A logical or system drive is that portion of a drive group seen by the host
`
`operating system as a single logical device. There can be more than one logical
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`drive associated with a particular drive group. A user creates a logical drive by
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`indicating the portions of the drive group that will be part of a particular logical
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`drive. For example, as shown in Fig. 5, drive group A includes three physical drives
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`150, 152, 154 and three logical drives A0, A1, and A2. Logical drive A0 spans across
`
`a designated portion of each physical drive 150, 152, and 154 in drive group A.
`
`Similarly, logical drive A, and A2 each span across a designated portion of each
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`physical drive 150, 152, and 154 in drive group A.
`
`Each logical drive within a drive group is ordered. This order is derived
`
`from the manner in which the logical drives are created. The logical drives are
`
`created based on the order of their respective drive groups. For instance, the first
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`logical drive created in the first drive group is considered the first logical drive, the
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`second logical drive created in the first drive group is considered the second logical
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`drive, and so on. As noted above, the order is used to define the logical drive that
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`serves as the boot drive. A boot drive is used at system initialization to boot up the
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`physical drives in the configuration. The first logical drive (i.e., logical driveo) is
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`considered the boot drive. In addition, the order is used to add disk capacity which
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`is discussed in more detail below. As shown in Fig. 5, logical A0 is considered the
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`first logical drive or boot drive of drive group A, logical drive A1 is considered the
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`second logical drive, and logical drive A3 is considered the third logical drive.
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`10
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`Each logical drive is configured by defining a capacity, a cache write policy,
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`and a RAID level. The capacity of a logical drive includes any portion of a drive
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`group up to the total capacity of that drive group.
`
`The RAID controller 102 has a cache memory 126 that is used to increase the
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`performance of data retrieval and storage operations. The cache memory 126 can be
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`operated in a write-back or write-through mode. In a write-back mode, write data is
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`temporarily stored in the cache 126 and written out to disk at a subsequent time. An
`
`advantage of this mode is that it increases the control1er’s performance. The RAID
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`controller 102 notifies the operating system that the write operation succeeded
`
`although the write data has not been stored on the disk. However, in the event of a
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`system crash or power failure, data in the cache 126 is lost unless a battery backup is
`
`used.
`
`In write-through mode, write data is written from the cache 126 to the disk
`
`before a completion status is returned to the operating system. This mode is more
`
`secure since the data is not lost in the event of a power failure. However, the write-
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`through operation lowers the performance of the controller 102 in many
`
`environments.
`
`Each logical drive has a RAID level which is based on the number of drives
`
`in the drive group in which it is created. In a preferred embodiment, the following
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`RAID levels are supported:
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`RAID LEVEL or JBOD
`
`DESCRIPTION
`
`RAID 1
`
`RAID 3
`
`RAID 5
`
`_
`
`Striping. Requires a minimum of 2 drives and a
`maximum of 8 drives. This RAID level does not
`
`support redundancy.
`
`Mirroring. Requires 2 drives. This RAID level
`supports redundancy.
`
`Requires a minimum of 3 drives and a maximum of
`8 drives. This RAID level supports redundancy.
`
`Requires a minimum of 3 drives and a maximum of
`8 drives. This RAID level supports redundancy.
`
`Combination of RAID 0 (striping) and
`RAID 1 (mirroring). Requires a minimum of 3
`drives and a maximum of 8 drives. This RAID
`
`level supports redundancy.
`
`Just a Bunch of Disks
`(JBOD)
`
`Each drive functions independently of one another.
`No redundancy is supported.
`TABLE I
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`Fig. 6 illustrates an exemplary assignment of the RAID levels for a particular
`
`drive group, drive group B. In this example, logical drive B0 spans across three
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`physical drives 156, 158, 160 and logical drive B1 spans across the same physical
`
`drives 156, 158, 160. Logical drive B0 is assigned RAID level 5 and logical drive B1
`
`is assigned RAID level 0+1.
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`Once the configuration procedure is completed, the configuration for each
`
`drive group is stored in each physical drive in a configuration file 134 preferably
`
`located in the last 64K bytes of the drive (step 178). The logical drives are then
`
`initialized (step 180) and the RAID controller 102 presents the configuration to the
`
`host operating system (step 182).
`
`The foregoing description has described the steps that can be used by a user
`
`to manually configure the disk drives connected to a RAID controller and introduces
`
`the terminology used in a preferred embodiment of the present invention. Attention
`
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`12
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`now turns to the methods and procedures that are used to automatically configure the
`
`disk drives connected to a RAID controller.
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`There are two procedures that are used to automatically configure the disk
`
`drives 110 connected to a RAID controller 102. A startup configuration procedure
`
`128 is used when the controller 102 is powered up or started before the operating
`
`system is operational. A runtime configuration procedure 130 is used to alter the
`
`configuration at runtime when additional disk drives are connected to the controller
`
`102. At runtime, the RAID controller 102 is operational and servicing the I/O
`
`activity.
`
`Fig. 7 illustrates the steps used by the startup configuration procedure 128 to
`
`create a configuration for the disk drives connected to the controller 102. At power-
`
`up, the controller 102 scans all the devices 110 connected to it in order to obtain the
`
`physical capacity of a disk drive and to obtain the configuration data from the disk
`
`drive (step 200).
`
`Fig. 8 illustrates this step (step 200) in further detail. The startup
`
`configuration procedure 128 scans each SCSI channel 106 (step 202) and each
`
`device 110 connected to the SCSI channel 106 (step 204). In a preferred
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`embodiment, the startup configuration procedure 128 can issue the SCSI command
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`TEST READY UNIT to determine if a peripheral connected to a SCSI charmel 106
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`is powered up and operational. The startup configuration procedure 128 can also
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`issue an INQUIRY command to determine the type of the peripheral device 110. If
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`the device 110 is not a disk drive (step 206-N), then the startup configuration
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`procedure 128 continues onto the next device 110. Otherwise (step 206-Y), the
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`startup configuration procedure 128 obtains the capacity of the disk drive (step 208).
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`This can be accomplished by the startup configuration procedure 128 issuing a
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`READ CAPACITY command to the device. The READ CAPACITY command
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`returns the maximum logical block address (LBA) for a disk drive which serves as
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`an indicator of the capacity of the device 110.
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`Next, the startup configuration procedure 128 attempts to read the
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`configuration file 134 stored in the disk drive (step 210). As noted above, the
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`configuration file 134 is preferably located at the last 64K block on the disk drive.
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`A configuration file 134 is present if the disk has been previously configured.
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`Otherwise, the configuration file 134 will not exist. The configuration file 134
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`contains configuration information such as the drive group identifier, the logical
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`drive identifier, the RAID level, as well as other information.
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`The startup configuration procedure 128 repeats steps 202 - 210 for each disk
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`drive 110 located on each channel 106 that is connected to the RAID controller 102.
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`Referring back to Fig. 7, the startup configuration procedure 128 then
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`analyzes the configuration information (step 212). The startup configuration
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`procedure 128 uses the configuration information to determine the validity of each
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`configuration and to determine which devices have not been configured.
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`A complete configuration is one where all the physical drives identified in
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`the configuration are connected to the controller 102. A partial configuration is one
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`where some of the physical drives identified in the configuration are not connected
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`to the controller 102. A valid configuration is one that is either a complete
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`configuration or a partial configuration where the logical drives are at least in the
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`degraded mode. Degraded mode refers to the situation where the following two
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`conditions are met. Firstly, the logical drives are configured with redundancy (i.e.,
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`RAID level 1, 3, 5, or 0+1) and secondly, a physical drive is dead or not operational
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`but the logical drive can still operate without any data loss. In degraded mode, the
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`drive group is fiinctioning and all data is available, but the array cannot sustain a
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`further drive failure without potential data loss.
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`After analyzing the configuration information, the startup configuration
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`procedure 128 determines whether there are any partial configurations present (step
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`214). As noted above, a partial configuration is one where some of the physical
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`drives identified in the configuration are not connected to the controller 102. If so
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`(step 214-Y), the startup configuration procedure 128 performs corrective actions to
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`configure the drive group as a valid configuration (step 216). The procedure 128
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`will attempt to place the logical drives in the degraded mode (step 216).
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`When the corrective action cannot be performed (step 218-N), the startup
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`configuration procedure 128 terminates processing and an appropriate error message
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`can be displayed to the user (step 220). In the case where the corrective action is
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`successful (step 218—Y), the startup configuration procedure 128 continues
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`processing.
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`The startup configuration procedure 128 then determines whether there are
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`any unconfigured drives (step 222). An unconfigured drive is one that does not have
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`a configuration file 134 associated with it. If there are any unconfigured drives, the
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`startup configuration procedure 128 configures the drives with the following
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`configurable default parameter settings (step 224):
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`Stripe size: The stripe size is the size of the amount of data written on one
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`drive before moving to the next drive. The stripe size is used to tune the controller
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`perfonnance for a specific environment or application. Typically, a smaller stripe
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`size provides better performance for random I/O and a larger stripe size provides
`better performance for sequential transfers.
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`Cache line size: The cache line size represents the size of the data that is
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`read or written. The cache line size is based on the stripe size.
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`SCSI transfer rate: The SCSI transfer rate sets the maximum transfer rate
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`for each drive charmel.
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`Spin-up option: The spin-up option controls how the SCSI drives in the
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`array are started. There are two spin-up modes that may be selected: Automatic and
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`On Power. The Automatic option causes the controller to spin-up all connected
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`drives, two-at-a—time at six second intervals, until every drive in the array is
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`spinning. The On Power option assumes that all drives are already spinning.
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`Controller read ahead: The controller read ahead option allows the
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`controller to read into the cache a full cache line of data at a time. When this option
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`is enabled, the percentage of cache hits is improved.
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`Automatic add capacity: This option automatically adds capacity to a
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`logical drive.
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`In addition, the startup configuration procedure 128 associates a RAID level
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`with the unconfigured drives based on the following parameter settings and the
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`number of inserted unconfigured drives (step 224). The parameter settings that are
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`used to affect the determination of the RAID level are as follows:
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`Redundancy: This option specifies whether or not data redundancy is
`
`required.
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`Redundancy method: This options specifies one of the two redundancy
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`methods: mirroring or parity. Mirroring refers to the 100% duplication of data on
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`one disk drive to another disk drive. Parity or rotated XOR redundancy refers to a
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`method of providing complete data redundancy while requiring only a fraction of the
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`storage capacity of mirroring. For example, in a system configured under RAID 5,
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`all data and parity blocks are divided between the drives in such a way that if any
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`single drive is removed or fails, the data on it can be reconstructed using the data on
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`the remaining drives.
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`Spare disposition: The controller allows for the replacement of failed hard
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`disk drives without the interruption of system service. A hot spare is a standby drive
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`that is used in the event of a disk failure to rebuild the data on a failed disk.
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`A RAID level is assigned to the unconfigured drives based on the
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`aforementioned parameter settings and the number of inserted unconfigured drives
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`in accordance with the following rules which are illustrated in Table II below:
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`(1) If the number of unconfigured drives = 1, then the unconfigured drive is
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`a JBOD.
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`(2)
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`If redundancy is not needed, the RAID level is set to RAID 0.
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`(3)
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`If redundancy is not needed and the number of drives = 2, then the
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`RAID level is set to RAID 1.
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`(4)
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`If redundancy is not needed, the number of drives >=