Seagate ST34572WC Spezifikationen PDF herunterladen (Seite 7)

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 reinstall a minimal system, restore a backup, and be back online within three

hours of diagnosis and replacement of hardware.

Three disks in the root volume group are better than two due to quorum restrictions. With a two-disk

root volume group, a loss of one disk can require you to override quorum to activate the volume

group; if you must reboot to replace the disk, you must interrupt the boot process and use the –lq

boot option. If you have three disks in the volume group, and they are isolated from each other

such that a hardware failure only affects one of them, then failure of only one disk enables the

system to maintain quorum.

• Keep your other volume groups small, if possible. Many small volume groups are preferable to a

few large volume groups, for most of the same reasons mentioned previously. In addition, with a

very large volume group, the impact of a single disk failure can be widespread, especially if you

must deactivate the volume group. With a smaller volume group, the amount of data that is

unavailable during recovery is much smaller, and you will spend less time reloading from backup. If

you are moving disks between systems, it is easier to track, export, and import smaller volume

groups. Several small volume groups often have better performance than a single large one. Finally,

if you ever have to recreate all the disk layouts, a smaller volume group is easier to map. Consider

organizing your volume groups so that the data in each volume group is dedicated to a particular

task. If a disk failure makes a volume group unavailable, then only its associated task is affected

during the recovery process.

• Maintain adequate documentation of your I/O and LVM configuration, specifically the outputs from

the following commands:

Command

Scope

Purpose

ioscan –f

Print I/O configuration

lvlnboot -v

for all volume

groups

Print information on root, boot, swap, and dump

logical volumes

vgcfgrestore –l

for all volume

groups

Print volume group configuration from backup file

vgdisplay –v

for all logical

volumes

Print volume group information, including status of

logical volumes and physical volumes

lvdisplay –v

for all logical

volumes

Print logical volume information, including

mapping and status of logical extents

pvdisplay –v

for all physical

volumes

Print physical volume information, including status

of physical extents

ioscan –m lun

(11i v3 onwards)

Print I/O configuration listing the hardware path

to the disk, LUN instance, LUN hardware path

and lunpath hardware path to the disk

With this information in hand, you or your HP support representative may be able to reconstruct a

lost configuration, even if the LVM disks have corrupted headers. A hard copy is not required or

even necessarily practical, but accessibility during recovery is important and you should plan for

this.

 Make sure that your LVM configuration backups are up-to-date. Make an explicit configuration

backup using the vgcfgbackup command immediately after importing any volume group or

activating any shared volume group for the first time. Normally, LVM backs up a volume group

configuration whenever you run a command to change that configuration; if an LVM command

prints a warning that the vgcfgbackup command failed, be sure to investigate it.

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