Product Description
IBM 2741 PCI RAID Disk Unit Controller
- SCSI RAID Controller
IBM 2741 is an Ultra SCSI disk and tape controller with a 4MB write-cache that provides RAID-5 protection for internal disk units. #2741 controls Ultra, Fast Wide and Fast Narrow SCSI disk and tape units that are installed in a base system unit and the #5064/#9364: System Unit Expansion with #9329: Expansion Unit for PCI cards. In addition to providing RAID-5 protection for disks, #2741 is also designed to work as a high performance controller for disks protected by system mirroring or disks with no protection. In the RAID-5 configuration, disk unit protection is provided at less cost than mirroring, and with greater performance than system checksums. The #2741 controller supports a maximum of 15 drives. RAID-5 - A minimum of four drives of the same capacity are needed for a valid RAID-5 configuration. A maximum of three arrays are allowed per controller, with a maximum of 10 drives allowed per array. All drives in an array must be of the same capacity. Parity is spread across four drives for arrays of four to seven drives. Parity can be spread across either four or eight drives for arrays of eight to 10 drives. For systems started with eight to 10 drives in an array, the parity for that array will be spread across eight drives. For systems started with less than eight drives in an array and later upgraded to eight, nine, or 10 drives the raid function must be stopped and then started before the parity will be spread across eight drives. Data Compression - #2741 supports hardware disk compression, enabled by the integration of data compression hardware directly into the data-flow of the controller. Data is compressed and decompressed without intervention from the AS/400 system processor. Capacity gains may vary as a function of the compression algorithm and the characteristics of the data. Typically two times compression can be expected, with up to four times possible. The disk capacity gains from disk compression are not included in the maximum AS/400 model disk capacity limits. Disk compression can be used with or without BRMS Hierarchical Storage Management (HSM) as part of a total storage management strategy including high-performance disk, compressed disk, and tape automation. Compressed disks have the same disk subsystem availability options (i.e., RAID-5, mirroring) as uncompressed disks, with no additional restrictions. Disk compression is supported only in user auxiliary storage pools (user ASPs). The user selects which disk arms to compress via a new Disk Manager screen, and disk capacity screens reflect the projected disk capacity and the percent used. Due to the overhead of compression/decompression, and the variations in the length of data written to disk, the performance of compressed disk will in most cases be slower than uncompressed, high-performance disk drives. The #2741 also supports one CD-ROM and one internal tape unit when placed in a system unit. When placed in the #5064/#9364: System Unit Expansion, the #2741 can support up to three internal Tape/CD-ROM units. Prerequisite: System unit or #5064/#9364 with #9329. Bus Slots Required: One High-Speed PCI. Maximum: One of the following in the system unit: #2726: PCI RAID Disk Unit Controller, #2740: PCI RAID Disk Unit Controller, #2741: PCI RAID Disk Unit Controller, #9728: Base PCI Disk Unit Controller, One of the following in the #9329 #2726: PCI RAID Disk Unit Controller #2741: PCI RAID Disk Unit Controller. OS/400 V4R2 or later required. #2741 will be specified on all V4R2 orders when a PCI disk controller is required. The following disk units may be placed into RAID-5 arrays: #6807/#9707: 4.19GB Disk Unit, #6813/#8813: 8.58GB Disk Unit, #6817/#8817: 8.58GB Disk Unit, #6824/#8824: 17.54GB Disk Unit. The following tape units are supported by the #2741: #6381: 2.5GB 1/4-Inch Cartridge Tape, #6382: 4.0GB 1/4-Inch Cartridge Tape, #6383: 16GB l/4-Inch Cartridge Tape, #6385: 13GB 1/4-Inch Cartridge Tape, #6386: 25GB l/4-Inch Cartridge Tape.
