IBM i Series, Handbook

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I/O Adapters and Controllers
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I/O Adapters and Controllers
#4778/#9778 PCI RAID Disk Unit Controller
The #4778/#9778 is an Ultra2 SCSI adapter with a maximum compressed write cache size of
104 MB that provides RAID-5 protection and compression for internal disk units, as well as
supports internal tape units, CD-ROM, and DVD-RAM units. This new disk controller is
available on all 270 and 8xx models.
The #4778/#9778 supports both disk compression and enhanced modes. The mode of
operation is determined by a hardware jumper. The Ultra2 SCSI adapter #4778/#9778 is
shipped in enhanced mode, which enables compression of the write cache, while Extended
Adaptive Cache (a Read Cache Device is needed for Extended Adaptive Cache, see below) a
or RAID-protection are also supported. By moving the hardware jumper, the adapter will
function in disk compression mode, and you can start compression for selected drives under
control of the adapter.
In addition to providing RAID-5 protection for disks, the #4778/#9778 is also designed to work
as a high performance controller for disks protected by system mirroring or disks with no
protection.
The #4778/#9778 also supports the #4331 1.6 GB Read Cache Device, which is used by
Extended Adaptive Cache to provide increased performance. The Read Cache Device
(#4331) is supported only when #4778/#9778 is in enhanced mode.
The #4778/#9778 controller supports a maximum of 18 disk units.
Note: Due to system CEC and external tower disk unit cage SCSI bus designs, only the
Model 270 will have a suitable system configuration to allow 18 disk units to attach to a single
#4778. All other CEC/tower disk unit configurations will restrict the number of attaching disk
units to 15 or less.
Note: Requires OS/400 V5R1 or later.
#4748/#9748 PCI RAID Disk Unit Controller
The #4748/#9748 is an Ultra2 SCSI disk unit controller with a 26 MB write-cache that
provides RAID-5 protection for internal disk units and also supports internal tape and
CD-ROM units. The #4748/#9748 supports both compression and non-compression modes.
The mode of operation is determined by a hardware jumper, which is in the non-compression
mode position when shipped. By moving the hardware jumper, the controller functions in
compression mode.
In addition to providing RAID-5 protection for disks, the #4748/#9748 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.