126 iSeries and AS/400e System Builder
#4748 #4748 PCI RAID Disk Unit Controller–26 MB Cache
The #4748 is an Ultra2 SCSI controller with a 26 MB write-cache that provides RAID-5 protection and compression for
internal disk units and supports internal tape units and CD-ROM units. The #4748 supports both compression and
non-compression modes. The mode of operation is determined by a hardware jumper. The #4748 is shipped in
non-compression mode. By moving the hardware jumper, the controller functions in compression mode. In addition to
providing RAID-5 protection for disks, the #4748 can work as a high performance controller for disks protected by system
mirroring or disks with no protection. The #4748 also supports #4331 1.6 GB Read Cache Device, which provides
increased performance. The #4331 1.6 GB Read Cache Device is supported only when the #4748/#9748 is
not in
compression mode.
The #4748 does not support data compression on 35 GB disk units. The #4748 controller supports a maximum of 18 disk
units in the Model 270.
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 10 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 10 disk units. For systems started with eight to 10 disk units in an array, the parity
for that array is spread across eight disk units. For systems that are started with less than eight disk units in an array and
later MES upgraded to eight, nine, or 10 disk units, the RAID function must be stopped and then started before the parity
is spread across eight disk units.
The #4748 controls up to two removable media devices (internal tape, CD-ROM, or DVD-RAM).
Requires a long PCI card slot. Only one is allowed in system unit and is mutually exclusive with #9767 and #4778.
The #4748 is a Customer Install Feature.
The #4748 was withdrawn from marketing on for new orders on 02 July 2002. The #4748 remains available as the target
of feature conversions.
The #4748 was withdrawn from marketing on 21 November 2003. The recommended replacement is a #4778 PCI RAID
Disk Unit Controller.
#4778 #4778 PCI RAID Disk Unit Controller–104 MB Cache
The #4778 is an Ultra2 SCSI controller with a 104 MB write-cache that provides RAID-5 protection and compression for
internal disk units and supports internal tape units and CD-ROM units. The #4778 supports both compression and
non-compression modes. The mode of operation is determined by a hardware jumper. The #4778 is shipped in
non-compression mode. By moving the hardware jumper, the controller functions in compression mode. In addition to
providing RAID-5 protection for disks, the #4778 is also designed to work as a high performance controller for disks
protected by system mirroring or disks with no protection. The #4778 also supports the #4331 1.6 GB Read Cache Device,
which provides increased performance. The #4331 1.6 GB Read Cache Device is supported only when the #4748/#9748
is
not in compression mode.
The #4778 controller supports a maximum of 18 disk units in the Model 270. 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 10 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
10 disk units. For systems started with eight to 10 disk units in an array, the parity for that array is spread across eight disk
units. For systems that are started with less than eight disk units in an array and later MES upgraded to eight, nine, or 10
disk units, the RAID function must be stopped and then started before the parity is spread across eight disk units.
The #4778 controls up to two removable media devices (internal tape, CD-ROM, or DVD-RAM).
Requires long PCI card slot. Only one allowed in the system unit and is mutually exclusive with the #9767 and #4748.
Minimum operating system level: OS/400 V5R1
The #4778 is a Customer Install Feature.
The #4778 was withdrawn from marketing on 19 November 2004. Conversions to the #4778 remain available.
