IBM 6532 RAID Disk Unit Controller

• SCSI Disk Controller

IBM 6532 is an Ultra SCSI controller with a 4MB write-cache that provides RAID-5 protection for internal disk units. #6532 offers greater performance than: #6502: Disk Controller for RAID, #6512: Disk Unit Controller for RAID, #6530: Storage Device Controller. #6532 controls Ultra Fast Wide and Fast Narrow SCSI disk units installed in: #5058: Storage Expansion Unit, #5083: Storage Expansion Tower, #5064/#9364: System Unit Expansion w/ #9331: Exp Unit for SPD Cards. It will also control Ultra, F/W, and F/N SCSI disk units installed in the: #5052: Storage Expansion Unit, #5082: Storage Expansion Towers. However, to hardware limitations those disks will not be controlled at Ultra speeds. In addition to providing RAID-5 protection for disks, #6532 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 #6532 controller supports a maximum of 16 drives. A minimum of four drives of the same capacity are needed for a valid RAID 5 configuration. A maximum of four 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 ten drives. For systems started with eight to ten drives in an array the parity, for that array, will be spread across eight drives. For systems that are started with less than eight drives in an array and later upgraded to eight, nine or ten drives the RAID function must be stopped and then started before the parity will be spread across eight drives.