topic Re: Linux and Snapshot in Operating System - Linux

Linux and Snapshot

Benoît — Tue, 20 Jun 2006 05:23:56 GMT

Hi,

Is it possible to present a snapshot to more than one Linux AS 4 at a time (read-only mode)?
From EVA side, no problem.
But from Linux servers, I don't know ...
I heard that Linux needs to write something about the superblock on each filesystem so ...

Is it necessary to add GFS?
Is GFS supported in EVA environment?

Thanks

Re: Linux and Snapshot

Steven E. Protter — Tue, 20 Jun 2006 06:09:49 GMT

Shalom,

GFS is supported on EVA disk.

Linux LVM2 has a snapshot software feature that might meet the need. You'll need to reserve some disk space and read up on the details.

SEP

Re: Linux and Snapshot

Steven E. Protter — Tue, 20 Jun 2006 06:10:47 GMT

Shalom,

GFS is supported on EVA disk.

It should not be necessary to add GFS.

If you want to use Oracle RAC and have simultaneous writes to a db from two hosts, or simultaneous writes to the same file from two hosts, GFS is needed.

Linux LVM2 has a snapshot software feature that might meet the need. You'll need to reserve some disk space and read up on the details.

SEP

Re: Linux and Snapshot

Benoît — Tue, 20 Jun 2006 06:39:11 GMT

Maybe I need to explain a bit more.

Our first plan was to use 1 vdisk and about 4 snapshots of that vdisk to present to 4 linux servers, and mount it as read-only.

Problem is when we update the original vdisk, all 4 snapshot will grow 100%.
As we plan to use this system for several vdisk, we will reach 100% of the EVA very quickly.

So I wondered if we could make just one snapshot and present it to all 4 servers.

What is the best way to do it (from Linux side) to be supported?

Re: Linux and Snapshot

dirk dierickx — Wed, 21 Jun 2006 02:39:46 GMT

not sure if i understand your question 100%. if you have one fs that is mounted RW on one node, and you want to share this fs with X other nodes in RO mode, you don't need snapshots, you can just point them to the same fs on each node, _as long as they only require RO access !!_

Re: Linux and Snapshot

Benoît — Wed, 21 Jun 2006 02:59:33 GMT

Hi,

I need Snapshots because my 4 servers need access a point-in-time copy of datafiles.
They should not see modifications on original LUN until I decide a new point-in-time copy.

So I want to present the VDisk to one server.
Make one Snapshot.
Present this Snapshot to 4 servers.
Mount the FS on 4 servers.

I don't know if that is supported, if that is supported RO or RW, and is that needs GFS.

Thanks for your answer.

Re: Linux and Snapshot

Thomas Callahan — Thu, 22 Jun 2006 08:33:40 GMT

Just take the snapshot, and zone so that all systems needed can see the snapshot. Scripting can do this.

Make sure your Linux machines are mounting RO. Not completely difficult, although I've never actually tried this scenario specifically.

Thanks,
Tom Callahan

Re: Linux and Snapshot

Benoît — Thu, 22 Jun 2006 08:48:23 GMT

Steven,

Do you have any matrix with GFS support?

Thanks