LVM Online Disk Replacement (LVM OLR)

ManualsBrandsHP ManualsSoftwareHP-UX 11i Volume Management (LVM/VxVM) Software

Abstract........................................................................................................................................2

Overview......................................................................................................................................2

Commands....................................................................................................................................4

Pvchange(1M)............................................................................................................................4

Detaching a path.....................................................................................................................4

Detaching a physical volume.....................................................................................................4

Attaching a path .....................................................................................................................4

Vgcfgrestore(1M)........................................................................................................................4

Initializing a replaced disk........................................................................................................4

Procedures....................................................................................................................................5

Before using LVM OLR: A Cautionary Note......................................................................................5

Isolating a troublesome device in an active volume group ..................................................................5

LVM Online Disk Replacement Procedure ........................................................................................6

Replacing an LVM disk in a Serviceguard cluster volume group...........................................................8

When replacing a disk requires halting applications and restoring data from a backup..............................9

Determining whether LVM OLR is available on the system....................................................................10

LVM OLR Messages......................................................................................................................11

pvchange(1M).......................................................................................................................... 11

vgcfgrestore(1M).......................................................................................................................11

Syslog Messages ......................................................................................................................12

For More Information ....................................................................................................................13

Call to action...............................................................................................................................13

Summary of content (14 pages)

PAGE 1
LVM Online Disk Replacement (LVM OLR) Abstract ........................................................................................................................................ 2 Overview ...................................................................................................................................... 2 Commands.................................................................................................................................... 4 Pvchange(1M) .......................
PAGE 2
Abstract The LVM Online Disk Replacement (OLR) feature provides new methods for replacing or isolating path components or LVM disks within an active volume group: v Using new commands options, LVM OLR enables the system administrator to follow a simpler procedure for replacing disks in an active volume group. The procedure does not require deactivating the volume group, modifying the volume group configuration or moving any user data.
PAGE 3
safely without interference or complaints from LVM. Detached devices remain that way until they are attached again using pvchange(1M), or until the volume group is reactivated using vgchange(1M). Detached devices are automatically attached the next time the volume group is activated or when the system is rebooted. Data Availability Considerations Clearly, detaching a failed disk has no effect on data availability, since the data on the disk was lost earlier when the disk failed.
PAGE 4
Commands Pvchange(1M) Detaching a path pvchange –a n dev The pvchange(1M) command provides a new –a n option that allows detaching the device associated with a specific path to a disk. Detaching the active path to a multiported device causes LVM to begin using an alternate path to the disk, if one is available and configured. If there are alternate paths to the disk that are still attached, the disk may still be in use by LVM even when the specified path is not.
PAGE 5
Procedures Before using LVM OLR: A Cautionary Note Before resorting to disabling or replacing a disk or path, it is important to be certain of the status of all the disks in the volume group, and to carefully consider the alternatives. Detaching the wrong path or disk can have unintended consequences. Refer to the LVM whitepaper When Good Disks Go Bad: Dealing with Disk Failures under LVM for a description of different disk failure scenarios and how best to handle them.
PAGE 6
LVM Online Disk Replacement Procedure Devices that are hot-replaceable can be replaced online using the LVM OLR feature without deactivating the volume group or changing the volume group configuration. 1. Prepare to replace a failed disk: Determine if there are unmirrored logical volumes on the disk or any mirrored logical volumes that may have been compromised due to simultaneous failures. Halt any applications and unmount any file systems using these logical volumes.
PAGE 7
6. Attach each path to the device using a new pvchange(1M) command option: pvchange -a y path After processing the pvchange(1M) command, LVM will resume using the device if possible. If it is desirable to attach all the paths in the entire volume group at once, this step can be skipped, step 7 would suffice to bring all the replaced devices online again. 7.
PAGE 8
Replacing an LVM disk in a Serviceguard cluster volume group Replacing LVM disks in volume groups in a Serviceguard cluster follows a similar procedure to the one described earlier except that if the volume group is shared, the commands to attach and detach the disks and paths must be executed individually on each of the cluster nodes sharing the volume group. Special care is required when performing a Serviceguard rolling upgrade.
PAGE 9
When replacing a disk requires halting applications and restoring data from a backup Replacing a disk requires halting applications and restoring data from a backup under the following circumstances: v If the disk being replaced contains any unmirrored logical volumes v If any data in the mirrored logical volumes on the disk being replaced has been compromised due to simultaneous disk failures If any of the logical volumes on the disk being replaced are not mirrored, the disk being replaced held the only co
PAGE 10
Determining whether LVM OLR is available on the system The feature is available in LVM patches for HP-UX 11.11 and 11.23. Both command and kernel components are required to enable the feature: o For 11.11: Patches PHKL_31216 and PHCO_30698 (or superseding patches) o For 11.23: Patches PHKL_32095 and PHCO_31709 (or superseding patches) LVM OLR will also be available in the next HP-UX release after 11.23 (11i V2).
PAGE 11
LVM OLR Messages pvchange(1M) 1. Usage: pvchange [-A Autobackup] [-s] | {[-S Autoswitch] [-x Extensibility] [-a Availability] [-t IOTimeout] [-z SparePV]} PhysicalVolumePath “a”: Illegal option. This error is reported when pvchange(1M) –a y is attempted on systems that do not have LVM OLR available. 2. The HP-UX kernel running on this system does not provide this feature. Install the appropriate kernel patch to enable it.
PAGE 12
vgcfgrestore(1M) then attached again (without replacing the disk). This causes LVM to reinitialize the disk and synchronize any mirrored user data mapped there. Syslog Messages 1. LVM: VG 64 0x010000: Data in one or more logical volumes on PV 188 0x072000 was lost when the disk was replaced. This occurred because the disk contained the only copy of the data. Prior to using these logical volumes, restore the data from backup.
PAGE 13
For More Information To learn more about LVM and HP-UX system administration, refer to the following documents on the HP documentation website (http://docs.hp.com): • Managing Systems and Workgroups http://docs.hp.com/en/5990-8172/index.html • When Good Disks Go Bad: Dealing with Disk Failures under LVM http://docs.hp.com/en/5991-1236/When_Good_Disks_Go_Bad.pdf Call to action HP welcomes your input.
PAGE 14
© 2005 Hewlett-Packard Development Company, L.P. The information contained herein is subject to change without notice. The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein.