I/O Adapter
258 AS/400e System Handbook
#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.
The #4748/#9748 controller supports a maximum of 18 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, with a maximum of ten drives allowed per array. All drives in an array must be of the
same capacity.
The #4748/#9748 also supports two removable media devices. This feature supports the
#4331 1.6 Gb Read Cache Drive for increased performance. The Read Cache Drive #4331 is
only supported in non-compression mode.
#9767 PCI Disk Unit Controller
The #9767 is an Ultra2 SCSI disk unit and removable media device controller.
The #9767 is the default controller in the Model 270 and controls up to six disk units and up to
two removable media devices (internal tape or CD-ROM).
The #9767 is the default controller in the Model 820 when RAID (#0041 Device Parity
Protection-All) is not on the order and controls up to six disk units and up to two removable
media devices (internal tape or CD-ROM).
#2749 PCI Ultra Magnetic Media Controller
The #2749 is an Ultra SCSI controller for attachment of an external tape device or an external
optical device.
Devices supported by #2749:
• 3490E
– C11/C22/C1A/C2A ½-inch Cartridge Tape Subsystem with #5040
– E01/E11 ½-inch Cartridge Tape Subsystem
– F00/F01/F11/F1A ½-inch Cartridge Tape Subsystem
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