HOT-Relocation
Process:
The hot-relocation feature is enabled by default.
No system administrator action is needed to start hot relocation when a failure
occurs.
The vxrelocd daemon starts during
system startup and monitors VxVM for failures involving disks, plexes, or
RAID-5 subdisks. When a failure occurs, vxrelocd triggers a hot-relocation
attempt and notifies the system administrator, through e-mail, of failures and
any relocation and recovery actions. The vxrelocd daemon is started by a
VxVM start-up script during system boot up. The argument to vxrelocd
is the list
of people to e-mail notice of a relocation (default is root). To disable vxrelocd, you can place a “#” in front of the line in
the corresponding start-up file.
A successful hot-relocation process involves:
1. Failure detection: Detecting the failure of a
disk, plex, or RAID-5 subdisk (The affected Volume Manager objects are
identified and the system administrator and other designated users are
notified.)
2. Relocation: Determining which subdisks
can be relocated, finding space for those subdisks, and relocating the subdisks
(The system administrator and other designated users are notified of the
success or failure of these actions. Hot relocation does not guarantee the same
layout of data or the same performance after relocation.)
3. Recovery: Initiating recovery
procedures, if necessary, to restore the volumes and data (Again, the system
administrator and other designated users are notified of the recovery attempt.)
How
is space selected for relocation?
A spare disk must be initialized and placed in a
disk group as a spare before it can be used for replacement purposes.
·
Hot
relocation attempts to move all subdisks from a failing drive to a single spare
destination disk, if possible.
·
If
no disks have been designated as spares, VxVM automatically uses any available
free space in the disk group not currently on a disk used by the volume.
·
If
there is not enough spare disk space, a combination of spare disk space and
free space is used. Free space that you exclude from hot relocation is not
used.
In all cases, hot relocation attempts to relocate
subdisks to a spare in the same disk group, which is physically closest to the
failing or failed disk. Note that if there is not enough free space, it is
possible for a subdisk to be relocated to multiple subdisks scattered to
different disks.
When hot relocation occurs, the failed subdisk is
removed from the configuration database. The disk space used by the failed
subdisk is not recycled as free space.
Marking/Unmarking a Disk as a Hot-Relocation Spare:
Syntax: # vxedit –g
diskgroup
set spare=on|off dm_name
To designate a disk as a spare
For Example
# vxedit –g rootdg
set spare=on rootdg06
# vxdisk list
DEVICE TYPE DISK GROUP STATUS
c2t0d0s2 auto:hpdisk rootdisk02 rootdg
online
c2t1d0s2 auto:LVM - - LVM
c3t2d0s2 auto:hpdisk rootdisk01 rootdg
online
c5t0d1 auto:cdsdisk rootdg02
rootdg online
c5t0d2 auto:cdsdisk rootdg03
rootdg online
c5t0d3 auto:cdsdisk rootdg04
rootdg online
c5t0d4 auto:cdsdisk rootdg05
rootdg online
c5t0d5 auto:cdsdisk rootdg06
rootdg online spare
c5t0d6 auto:cdsdisk rootdg07
rootdg online
c5t0d7 auto:cdsdisk rootdg08
rootdg online
c5t1d0 auto:cdsdisk rootdg01
rootdg online
Removing a Disk from User as a Hot-Relocation Spare
To make disk rootdg06
available for normal use:
# vxedit –g rootdg set
spare=off rootdg06
[rx26-159]/
# vxdisk list
DEVICE TYPE DISK GROUP STATUS
c2t0d0s2 auto:hpdisk rootdisk02 rootdg
online
c2t1d0s2 auto:LVM -
- LVM
c3t2d0s2 auto:hpdisk rootdisk01 rootdg
online
c5t0d1 auto:cdsdisk rootdg02
rootdg online
c5t0d2 auto:cdsdisk rootdg03
rootdg online
c5t0d3 auto:cdsdisk rootdg04
rootdg online
c5t0d4 auto:cdsdisk rootdg05
rootdg online
c5t0d5 auto:cdsdisk rootdg06
rootdg online
c5t0d6 auto:cdsdisk rootdg07
rootdg online
c5t0d7 auto:cdsdisk rootdg08
rootdg online
c5t1d0 auto:cdsdisk rootdg01
rootdg online
To Exclude or include a Disk from Hot-Relocation
Syntax: # vxedit –g
diskgroup
set nohotuse=on|off dm_name
# vxedit set spare=on rootdg06
# vxedit -g rootdg set nohotuse=off rootdg06
# vxdisk list
DEVICE TYPE DISK GROUP STATUS
c2t0d0s2 auto:hpdisk rootdisk02 rootdg
online
c2t1d0s2 auto:LVM - - LVM
c3t2d0s2 auto:hpdisk rootdisk01 rootdg
online
c5t0d1 auto:cdsdisk rootdg02
rootdg online
c5t0d2 auto:cdsdisk rootdg03
rootdg online
c5t0d3 auto:cdsdisk rootdg04
rootdg online
c5t0d4 auto:cdsdisk rootdg05
rootdg online
c5t0d5 auto:cdsdisk rootdg06
rootdg online spare
c5t0d6 auto:cdsdisk rootdg07
rootdg online
c5t0d7 auto:cdsdisk rootdg08
rootdg online
c5t1d0 auto:cdsdisk rootdg01
rootdg online
To force hot
relocation to only use spare disks:
Add
spare=only in /etc/default/vxassist
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