Seagate ST34572WC Specifications download pdf (Page 5)

# swlist -l fileset | grep -i mirror

LVM.LVM-MIRROR-RUN B.11.23 LVM Mirror

The process of mirroring is usually straightforward, and can be easily accomplished using the system

administration manager SAM, or with a single lvextend command. These processes are documented in

Managing Systems and Workgroups. The only mirroring setup task that takes several steps is mirroring the root

disk; for the recommended procedure for adding a root disk mirror, refer to

Appendix A: Procedures.

Three corollaries to the mirroring recommendation are:

1. Use the strict allocation policy for all mirrored logical volumes. Strict allocation forces mirrors to occupy

different disks. Without strict allocation, you can have multiple mirror copies on the same disk; if that disk

fails, you will lose all your copies. The allocation policy is controlled with the –s option of the lvcreate

and lvchange commands. By default, strict allocation is enabled.

2. To improve the availability of your system, keep mirror copies of logical volumes on separate I/O busses

if possible. With multiple mirror copies on the same bus, the bus controller becomes a single point of

failure—if the controller fails, you lose access to all the disks on that bus, and thus access to your data. If

you create physical volume groups and set the allocation policy to PVG-strict, LVM helps you avoid

inadvertently creating multiple mirror copies on a single bus. For more information about physical volume

groups, refer to lvmpvg(4).

3. Consider using one or more free disks within each volume group as spares. If you configure a disk as a

spare, then a disk failure causes LVM to reconfigure the volume group so that the spare disk takes the

place of the failed one. That is, all the logical volumes that were mirrored on the failed disk are

automatically mirrored and resynchronized on the spare, while the logical volume remains available to

users. You can then schedule the replacement of the failed disk at a time of minimal inconvenience to you

and your users. Sparing is particularly useful for maintaining data redundancy when your disks are not

hot-swappable, since the replacement process may have to wait until your next scheduled maintenance

interval. Disk sparing is discussed in

Managing Systems and Workgroups.

Creating Recovery Media

Ignite/UX enables you to create a consistent, reliable recovery mechanism in the event of a catastrophic failure of

a system disk or root volume group. You can back up essential system data to a tape device, CD, DVD, or a

network repository, and recover the system configuration quickly. While Ignite/UX is not intended to be used to

back up all system data, you can use it with other data recovery applications to create a means of total system

recovery.

Ignite/UX is a free add-on product, available from

www.hp.com/go/softwaredepot. Documentation is available

at the Ignite/UX

website.

Other Guidelines for Optimal System Recovery

Here are some other recommendations, summarized from Managing Systems and Workgroups, that simplify

recoveries after catastrophic system failures:

• Keep the number of disks in the root volume group to a minimum; no more than three, even if the root

volume group is mirrored. The benefits of a small root volume group are threefold. First, fewer disks in the

root volume group means less opportunities for disk failure in that group. Second, more disks in any

volume group leads to a more complex LVM configuration, which will be more difficult to recreate after a

catastrophic failure. Finally, a small root volume group is quickly recovered. In some cases, you can

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