cggibbo |Mar 31 2010| Comments (5) | Visits (30446)
1
Just the other day, I needed to use the AIX splitvg command in order to copy some data from one system to another.
I thought I’d share the experience here.
The splitvg command can split a single mirror copy of a fully mirrored volume group into a separate “snapshot” volume group.
From the man page:
The original volume group VGname will stop using the disks that are now part of the snapshot volume group SnapVGname. Both volume groups will keep track of the writes within the volume group so that when the snapshot volume group is rejoined with the original volume group consistent data is maintained across the rejoined mirrors copies. Notes:
So, looking at point 4, above, if you are using enhanced concurrent volume groups (for example with PowerHA), then you will not be able to use the splitvg command. This is disappointing as this would have been very handy in some of the large PowerHA systems I have worked with…..perhaps this will be supported in the future?
Anyway, back to my example. I had wanted to break-off one of the mirrors of a mirrored volume group and then assign the “split” volume group to another host to copy some data off.
The volume group datavg contained two disks, hdisk0 and hdisk3, as shown in the lspv output below.
# lspv
hdisk1 00c01c705bdc6136 old_rootvg
hdisk0 00c01c70c050810f datavg active
hdisk2 00c01c7018a47201 rootvg active
hdisk3 00c01c70fed9e41a datavg active
There were only two logical volumes (loglvl00, jfs2 log and fslv00, data) and a single file system (/data) in this volume group.
# lsvg -l datavg
datavg:
LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT
loglv00 jfs2log 1 2 2 open/syncd N/A
fslv00 jfs2 16 32 2 open/syncd /data
The volume group datavg, was mirrored across hdisk0 and hdisk3, as shown in the lsvg output below.
# lsvg -p datavg
datavg:
PV_NAME PV STATE TOTAL PPs FREE PPs FREE DISTRIBUTION
hdisk0 active 583 566 117..100..116..116..117
hdisk3 active 583 566 117..100..116..116..117
The logical volumes for the /data file system and the JFS2 log were both mirrored, as shown in the lslv/lspv output.
# lslv fslv00
LOGICAL VOLUME: fslv00 VOLUME GROUP: datavg
LV IDENTIFIER: 00c01c7000004c0000000122e9038480.2 PERMISSION: read/write
VG STATE: active/complete LV STATE: opened/syncd
TYPE: jfs2 WRITE VERIFY: off
MAX LPs: 512 PP SIZE: 256 megabyte(s)
COPIES: 2 SCHED POLICY: parallel
LPs: 16 PPs: 32
STALE PPs: 0 BB POLICY: relocatable
INTER-POLICY: minimum RELOCATABLE: yes
INTRA-POLICY: middle UPPER BOUND: 32
MOUNT POINT: /data LABEL: /data
MIRROR WRITE CONSISTENCY: on/ACTIVE
EACH LP COPY ON A SEPARATE PV ?: yes
Serialize IO ?: NO
# lslv loglv00
LOGICAL VOLUME: loglv00 VOLUME GROUP: datavg
LV IDENTIFIER: 00c01c7000004c0000000122e9038480.1 PERMISSION: read/write
VG STATE: active/complete LV STATE: opened/syncd
TYPE: jfs2log WRITE VERIFY: off
MAX LPs: 512 PP SIZE: 256 megabyte(s)
COPIES: 2 SCHED POLICY: parallel
LPs: 1 PPs: 2
STALE PPs: 0 BB POLICY: relocatable
INTER-POLICY: minimum RELOCATABLE: yes
INTRA-POLICY: middle UPPER BOUND: 32
MOUNT POINT: N/A LABEL: None
MIRROR WRITE CONSISTENCY: on/ACTIVE
EACH LP COPY ON A SEPARATE PV ?: yes
Serialize IO ?: NO
# lspv -l hdisk0
hdisk0:
LV NAME LPs PPs DISTRIBUTION MOUNT POINT
fslv00 16 16 00..16..00..00..00 /data
loglv00 1 1 00..01..00..00..00 N/A
# lspv -l hdisk3
hdisk3:
LV NAME LPs PPs DISTRIBUTION MOUNT POINT
fslv00 16 16 00..16..00..00..00 /data
loglv00 1 1 00..01..00..00..00 N/A
Using the splitvg command I was able to break-off one of the disks from the mirrored pair. This created a new volume group on hdisk3 called vg00.
# splitvg -c1 datavg
# lspv
hdisk1 00c01c705bdc6136 old_rootvg
hdisk0 00c01c70c050810f datavg active
hdisk2 00c01c7018a47201 rootvg active
hdisk3 00c01c70fed9e41a vg00 active
The new volume group contains a new logical volume (pre-fixed with fs i.e. fsfslv00) and a file system (pre-fixed with /fs i.e. /fs/data). I can mount this file system and access the data in the file system and create and/or modify files (as shown below).
# mount /fs/data
Replaying log for /dev/fsfslv00.
# cd /fs/data
# ls -ltr
total 112
drwxrwxrwx 2 root system 53248 Jan 30 2009 AIX61TL2SP2
drwxr-xr-x 2 root system 256 Aug 05 15:24 lost+found
-rw-r--r-- 1 root system 0 Sep 15 10:29 2
# touch 3
# ls -ltr
total 112
drwxrwxrwx 2 root system 53248 Jan 30 2009 AIX61TL2SP2
drwxr-xr-x 2 root system 256 Aug 05 15:24 lost+found
-rw-r--r-- 1 root system 0 Sep 15 10:29 2
-rw-r--r-- 1 root system 0 Sep 15 10:46 3
At this point I was able to export the volume group and import it on another system. I had to re-map the Virtual SCSI disk on my VIOS first.
# cd
# umount /fs/data
# varyoffvg vg00
# exportvg vg00
# rmdev –dl hdisk3
; Re-map the disk at the VIOS layer to the other AIX LPAR.
; Configure the disk on the other LPAR (with cfgmgr) and import the volume group (with importvg).
Once I was finished with vg00 on the other LPAR, I re-mapped the disk to the original AIX LPAR, configured the disk and then re-joined the disk to the datavg volume group, with the joinvg command.
; Export the VG and remove the disk on the other AIX LPAR.
; Re-map the disk at the VIOS layer to the original AIX LPAR.
# cfgmgr
# lsdev –Cc | grep hdisk3
hdisk3 Available Virtual SCSI Disk Drive
# joinvg datavg
# lspv
hdisk1 00c01c705bdc6136 old_rootvg
hdisk0 00c01c70c050810f datavg active
hdisk2 00c01c7018a47201 rootvg active
hdisk3 00c01c70fed9e41a datavg active
The volume group is now fully mirrored again. However the partitions are stale and need to be sync’ed. I manually re-sync the volume group with the syncvg command.
# lsvg -l datavg
datavg:
LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT
loglv00 jfs2log 1 2 2 open/stale N/A
fslv00 jfs2 16 32 2 open/stale /data
# syncvg –v datavg
# lsvg -l datavg
datavg:
LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT
loglv00 jfs2log 1 2 2 open/syncd N/A
fslv00 jfs2 16 32 2 open/syncd /data
More information can be found here: http://www-01.ibm.com/support/docview.wss?uid=isg3T1010934
Article Number: 597
Posted: Mon, Jun 3, 2019 2:26 PM
Last Updated: Mon, Jun 3, 2019 2:26 PM
Online URL: http://kb.ictbanking.net/article.php?id=597