Snapmirror to tape is pretty much your best bet. It's block based, and is reasonably fast for most situations. Definitely faster then anything that works on the filesystem (Qtree snapmirror, ndmp, dump, nfs...). You can't do single file restores, however. so if that's a requirement, you might be out of luck. Since snapmirror to tape is a mirror of a filesystem, to restore, you have to recover the entire filesystem. Which might be annoying. I know of a customer, who just has restore filers, that are used just for this purpose. They snapmirror to tape (SM2T), then if a request comes for old data that's been backed up, they restore to another filer, and pull the data out that way. Also, since it's snapmirror to tape, you deal with whole volumes, which can be quite large.
One very cool thing about snapmirror to tape, is it's ability to change geometry of the destination filer. So we can snapmirror to tape a volume from a F760 (let's say), with 36gig disks, but tell the process that you'll be restored to a R200's disk geometry. Then, when we restore, the data is properly layed out on the R200's spindles.
Hope that helps, -Blake
On 11/15/05, Ben Rockwood BRockwood@homestead-inc.com wrote:
I'm looking into various methods for tape backup of our filers. Due to the large number of files a file level backup would be significantly slower than a block-level backup method, however I'm not sure if one exists. I was hoping someone could clarify. NDMP utilizes dump, which is file-based so that doesn't solve the performance issues, and from what I can tell SnapVault is only for disk-to-disk backup, not tape. Even if I direct connect a tape robot to the filer I'd still be using dump and the throughput isn't being limited by the network capacity, so that doesn't help either.
I'm hoping there is a block-level method I'm unaware of. NDMP in my tests has been dog slow and standard backups via NFS mount don't sound appealing.
Suggestions are welcome.
benr.