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Back me up

The main selling point of SANs was the promised ability to do "offline backups". IOW since you have moved all of your data into one place, you should be able to back that stuff up to tape - in the background. Every sysadmin would welcome giving up the spaghetti mess that is backup administration! No more finding out that the only machine not being backed up was the one that just fell over . . .

This never happened. Not because it wasn't important - but because the design of SANs made it difficult (read impossible). Whereas a simple LAN can accommodate NFS drives (file-system access), there was no solution for block-level access. This was needed (supposedly) for large databases. So in order to provide this block-level "drive", the World Wide Number was born.

It is the limitation of the WWN that prevents SAN backups. A WWN from a drive can only be assigned to a specific HBA (or 2). In order to back up a SAN drive, you would need to add the backup server HBA WWN to ALL SAN drives. Then you would have to handle things like shared access and database quiescence. After all of that, you would still have to map the nameless drives into restoring a certain file for a certain server. That's a lot of crap to go through just to say you can back up SAN from the SAN.

So what happens is that each and every Virtual Machine needs its OWN copy of backup software, and the backups still go over the LAN - as they have since the beginning of time . . .

So I guess that there IS a cost for creating a VM. So what was that about taking the "load" off of the network? What a bunch of hooey.

Posted by: Roger Ramjet   Posted on: 01/06/09 You are currently: a Guest | Members login | Terms of Use

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