topic Connect to snapshot from a (Windows) server which is already connected to the parent volume? in StoreVirtual Storage

Connect to snapshot from a (Windows) server which is already connected to the parent volume?

TMTech Tony — Tue, 14 Feb 2012 14:44:13 GMT

I'm running SAN/IQ 9.0 on a 2-node cluster which I'm access via iSCSI. I have a large volume for my main file server and I want to take scheduled snapshots to use as an alternative to daily backups to tape. I already have several snaps and I can assign "Servers" to them and I have successfully connected to snapshots using my desktop (Windows 7 Pro) and a Backup Exec media server (Windows 2003).

What I would _like_ to do, however, is to connect to a snapshot using the file server (Windows 2008 R2) which is already connected to the parent volume of the snapshot. Unfortunately, I have not been able to see the snapshot from the file server -- the parent volume target is already connected and no amount of refreshing is showing me any additional targets. I have not yet been able to acquire a maintenance period in which I could disconnect from the main volume target and then try refreshing again -- and I don't really want to do that anyway, if I don't have to. And I shouldn't have to.

Am I missing something? Is there a problem with connecting to a snapshot using a server which is already connected to the snapshot's parent?

Any help much appreciated.

Tony

Re: Connect to snapshot from a (Windows) server which is already connected to the parent volume?

TMTech Tony — Tue, 14 Feb 2012 17:43:22 GMT

Following up on my on post, after speaking to an HP support engineer.

There is a fundamental issue I didn't know about: it is not possible for a server already connected to a snapshot's parent volume to also connect to the snapshot. The reason given was that the snapshots are "not very smart." The snapshot does not use a different volume ID (if I remember correctly) and so, a server already connected to the parent volume would get very confused if it were allowed to connect to the snapshot as well. I got the impression that the SAN prevents this from being a problem by preventing the snapshot from being presented to the server, if that server is already connected to the parent volume.

The recommended procedure for restoring files from a snapshot is to presnet the snapshot to another server (a "restore" server) and then copy files from the restore server back to the source server.

Re: Connect to snapshot from a (Windows) server which is already connected to the parent volume?

Paul Hutchings — Tue, 14 Feb 2012 18:36:44 GMT

Please don't take this the wrong way as you may have really good reasons for doing so, but I wouldn't normally consider SAN snapshots as a substitute for a proper "not on the SAN" backup, just as a compliment to existing backups.

Re: Connect to snapshot from a (Windows) server which is already connected to the parent volume?

Bart_Heungens — Wed, 15 Feb 2012 08:54:09 GMT

Hi,

This is a Windows specific issue, not SAN...

When Windows gets a volume attached, it will write a unique UIS or signature to the disk...

Since the snapshot contains the same signature, Windows will think it is the same volume... And so it is not possible to connect the same disk twice to the server...

What you can do is attach it to the backup server or even your Windows 7 laptop which has a build-in iSCSI initiator and recover the files that you need...

Kr,

Bart