Internal disk, tape, CD-ROM, DVD-RAM, DVD-ROM storage 387
Draft Document for Review October 18, 2004 5486IntStor.fm
RAID-5 protection is supported for all internal disks, provided that it is supported
by the disk controller. A RAID controller is required to support concurrent
maintenance.
Mirroring
Mirrored protection is a function that increases the availability of iSeries and i5
servers in the event of a failure of a disk-related hardware component. It can be
used on all iSeries servers. Software support is a part of the Licensed Internal
Code (LIC).
Different levels of mirrored protection are possible, depending on the hardware
that is duplicated. Mirroring involves duplicating disk-related hardware (bus, IOP,
disk device). When a disk-related mirrored component fails, the system remains
available.
Cross-site mirroring
Cross-site mirroring (XSM), combined with the geographic mirroring function,
enables you to mirror data on disks at sites that can be separated by a significant
geographic distance. This technology can be used to extend the functionality of a
device cluster resource group (CRG) beyond the limits of physical component
connection.
Geographic mirroring provides the ability to replicate changes made to the
production copy of an independent auxiliary storage pool (IASP) to a mirror copy
of that IASP. As data is written to the production copy of an IASP, the operating
system mirrors that data to a second copy of the IASP through another system.
This process keeps multiple identical copies of the data.
Integrated hardware disk compression
Data is dynamically compressed or uncompressed by the DASD controller as
data is written to and read from disk. Disk compression has no effect on the main
CPU utilization since compression is performed by the DASD controller
input/output processor (IOP).
Support for Integrated Hardware Disk Compression is provided by the #4748 PCI
RAID Disk Unit Controller or #4778/#9778 PCI RAID Disk Unit Controller
(withdrawn from marketing 19 November 2004).
The compression ratio results of DASD varies. The compression ratio achieved
and the impact on DASD performance depends on the data and how it is
accessed. Compression is limited to user auxiliary storage pools (ASPs).
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