Internal Magnetic Media
342 AS/400e System Handbook
#8818 Optional Base Two-Byte Disk Unit 17.54 GB 10k RPM Disk Unit Ultra
This feature provides 17.54 GB of high performance (10k RPM) disk capacity with an Ultra
SCSI (LVD) interface. This disk unit is not supported on disk controllers #6502/#6512/#6530.
#882417.54GBOptionalBaseTwo-ByteDiskUnit(UltraSCSI)
Provides a 3 ½-inch single disk unit with 17.54 GB capacity as an optional base disk.
#9606 1.967 GB Base Disk Unit
Provides a 3 ½-inch single disk unit with 1.967 GB capacity as base disk unit.
#9707 4.19 GB Base Two-Byte Disk Unit (Ultra SCSI)
Provides a 3 ½-inch single disk unit with 4.19 GB capacity as a PCI base disk unit.
#9907 4.19 GB Base Two-Byte Disk Unit (Ultra SCSI)
The default SPD base disk unit provides a 3 ½-inch single disk unit with 4.19 GB capacity.
Disk Protection
AS/400 disk drives can be protected by using several functions, which are discussed in the
following section.
Device Parity Protection
Device parity protection is a hardware function that protects data from being lost because of a
disk unit failure or damage to a disk. Calculating and saving a parity value for each bit of data
protects data. Conceptually, the parity value is computed from the data at the same location
on each of the other disk units in the device parity set. When a disk failure occurs, the data on
the failing unit can be reconstructed by using the saved parity value and the values of the bits
in the same locations on the other disk.
Device parity protection is a high-availability function. It allows the AS/400 system to continue
to operate when a single disk failure has occurred. The system continues to run in an
exposed mode until the repair operation is complete and the data is rebuilt. If a failure occurs,
you should correct the problem quickly. In the unlikely event that another disk fails, you can
lose data.
The base disk unit controller in the 9406 Model 250, Model 270, and Model 820 does not
support Device Parity Protection.
The disk array subsystems that are supplied by IBM enhance the selection of recovery
options available on the AS/400 system. This method of protection is based on the
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