lvsplit when the vg is in shared mode (OPS)

[Kiran Kumar Aekabote]

Hi

I want to know can we split the mirrored lv (raw),which is in disk array (12H). The mirrored lv is created on two physical disks(luns)in one VG. The VG is made OPS volume group and shared. The entire setup is in two node cluster.

I have created lv like following:
lvcreate -m 1 -M n -c y -n lvtestsp -L 52 /dev/vgxx
once creating the lv exported the map file and imported onto another node, later activated the vg in shared mode.

On the first node when i try to split the lv, the message is displayed saying lvsplit can not be done on a shared volume group.

When i try to activate the vg on second node, the message is displayed as software mirror is not possible on shared volume groups.

Will really possible to split the lv's on OPS shared volume group? if possible how ?

Thanks

[Stefan Farrelly]

I think you need to made the VG not shareable on the source node first (not the second node). You need to deactivate it (-a n) then vgchange -S n. Then you can split and make it shareable again (-S y) then reactivate it.

[Kiran Kumar Aekabote]

Hi Stephen

I would like to split the lv when the volume group is active and in shared mode.

[Stefan Farrelly]

sorry, I dont think you can. You must deactivate it and remove it from shared mode before you can split it.

[Kiran Kumar Aekabote]

Hi

I further extened the above, i want to split the mirror lvs( SHARED OPS), which are created for oracle 9i RAC, implemented in two node cluster. When i try to split the mirror, the message is "cannot perform configuration change when vg is active in shared mode".

Previously when i try to split the same the messge was software mirros cannot support on shared mode. This was solved after applying the patch PHKL_27178 on 11.0.

As the ORACLE instance must and should run, mean time i want to split the lvs for backup and merge them once backups is completed.

Will the split support on 11i ?

Thanks

[Hemanth Gurunath Basrur]

Hello Kiran,

Refer to the following links for info.

http://forums1.itrc.hp.com/service/forums/bizsupport/parseCurl.do?CURL=%2Fcm%2FQuestionAnswer%2F1%2C%2C0x9ad0506d69a7d711abdc0090277a778c%2C00.html&forumId=2&admit=716493758+1066562590034+28353475

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=4843

http://ark.sourceforge.net/hp-mirror-ux.html

Hope this helps.

Regards,
Hemanth

[Rita C Workman]

You can do this, but please take a good look at the threads above you were pointed to. Paula makes a very important point. If you are planning on splitting a mirrored set of disks than you place your data in jeopardy until the mirror gets refreshed.

A way around this is to add a third mirror (in some configurations called a Business Continuance Volume) and then split off just the third mirror for backups, etc. By doing this your data stays far more secure.

Yes it is more costly, but loss of data may be far more costly...

Regards,
Rita

[Kiran Kumar Aekabote]

Hi Hemanth / Rita

Basically i am not looking at how to split lvs. As i was already mentioned that i am using OPS volume group shared accross 2 nodes. I want to split the lvs of OPS VG when they are "active" and "shared mode".

When i try to split the mirror lv when cluster is up on 2nodes, and vg is active and shared across 2nodes, message is displayed as under "cannot perform configuration change when vg is active in shared mode"

I know about the Business copy. Without using Business copy is it possible ?

[Kiran Kumar Aekabote]

Hi

Any body have any solution for the above? Please post your views/solutions.

once again the question: Is lvsplit possible when the vg(OPS) is active in shared mode on a 2node cluster.

Thanks
Kiran

[Rita C Workman]

We split active groups within our MC/SG cluster all the time. Of course we use BCV disks and that is what we copy/split off.
These BCV's are 'connected' via software to the mirrored pair of disks (we use EMC), creating a third mirror. In effect, we keep these disks 'hidden' from everyone. Then we put our database in hotbackup and split off the BCV only. This is how we control the copying of large amounts of data from one site to another. For smaller we just mirror across and split the two sets of mirrored pairs apart, with the 2nd set having a BCV connected to it. It is then this BCV that we split off and mount for backups.

But like I said, doing all this required another piece of software and obviously more disk.

Hope this gives you some ideas, and let me repeat that I (like Paula) do not recommend splitting a mirrored pair in half to run backups on. That is just too much time out of sync....and the disk that goes is always the production disk (Murphy's Law)

Rgrds,
Rita

[Kiran Kumar Aekabote]

Hi Rita

I want to know, whether i can split the lvs without BVC?

Thanks
Kiran

[Rita C Workman]

From an lvm perspective...I do not believe you can split active/shared mirrored disks. I think Stephen mentioned that...you would have to pull them out of their present shared/active status before you could split them (as they are)...

Sorry...to do what you are wanting seems to require something along the line of a BCV..

Rgrds,
Rita