iSeries IBM 9406, #4778 PCI RAID Disk Drive / DASD CTLR
(#4778 / #9778) PCI RAID Disk Unit Controller
(Only available as REFURBISHED as of November 21, 2003)
The #4778/#9778 is an Ultra2 SCSI controller with a maximum compressed write cache size of 104MB that provides RAID-5 protection and compression for internal disk units and also internal tape units, CD-ROM and DVD-RAM units.
#4778 is an optional disk unit controller for Models 820, 830, and 840.
#9778 is the base disk unit controller on Models 830 and 840.
#4778/#9778 support both disk compression and enhanced modes. The mode of operation is determined by a hardware jumper. It is shipped in enhanced mode, which enables compression of the write cache and Extended Adaptive Cache (feature #4331, 1.6GB Read Cache Device, is needed for the OS/400 Extended Adaptive Cache function.) By moving the hardware jumper, the controller will function in disk compression mode.
In addition to providing RAID-5 protection for disks, #4778/#9778 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 #4778/#9778 controllers support a maximum of 15 disk units.
A minimum of four disk units 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 ten disk units allowed per array. All disk units in an array must be of the same capacity. Parity is spread across four disk units for arrays of four to seven disk units. Parity can be spread across either four or eight disk units for arrays of eight to ten disk units. For systems started with eight to ten disk units in an array the parity, for that array, will be spread across eight disk units. For systems that are started with less than eight disk units in an array and later field upgraded to eight, nine, or ten disk units, the RAID function must be stopped and then started before the parity will be spread across eight disk units.
The #4778/#9778 controls up to two removable media devices (internal tape, CD-ROM or DVD-RAM).
Prerequisite: Available PCI slot under a base or optional feature PCI IOP. OS/400 V5R1, or later is required.
Supported on the following systems: 270, 520, 550, 570, 595, 800, 810, 825, 870, 890