Over at SearchStorage, there’s an article at the moment about using NAS disk as a disk backup target – i.e., where (in NetWorker), the ADV_FILE device would be created.
I have to say, I strongly disagree with the notion of using NAS mounted filesystems for disk backup, even if NetWorker lets you. In short, it’s a very bad idea, and primarily for performance reasons.
Consider this – the optimal backup configuration for NAS is to use NDMP wherever possible; otherwise, if we backup the volume(s) as they are mounted on another host, every backup involves a double network transfer – once to retrieve the data from the NAS device to the mounter, and then a second transfer to have the backup product copy the data from the mounter to backup storage.
So, let me ask the obvious question – if performance issues act as a primary reason to not backup NAS via mounts, are there any compelling performance reasons why the reverse would be acceptable?
I don’t believe there are. If wishing to use array presented storage for disk backup, it would be far more advisable to use SAN storage, where the volume(s) are presented and attached as just another form of local storage.
Backing up to NAS is one of those activities that falls into the realm of “just because you can do something doesn’t mean you should do it.”
[Edit, 2009-11-15]
In recent discussions with a couple of vendors, I’m willing to entertain the notion that backing up to NAS may be acceptable in an enterprise environment, but my caveat would still be a dedicated 10 Gbit ethernet link between the NAS server and the backup server.
