Generally the backup software keeps track of and takes care of that.
Say you back up /vol/myvol using a level0 (full) on Sunday, then increasing daily levels over the week (L1 on Monday, L2 on Tuesday, etc.) until you do another level0 next Sunday again. Then, you discover that /vol/myvol/importantdirectory was accidentally deleted last Wednesday.
You tell the backup software "restore /vol/myvol/importantdirectory as of Wednesday"; the backup software should then scan through the file indexes it keeps, then restore importantdirectory from the level0, level1, level2, and level3 (Wed. AM, before the deletion) backups.
This requires the backup software to keep track of the file index data sent to it by the filer, which it may not be doing (I'm not familiar with NetVault). You also typically need to have the backup software tell the filer to send it the indexes, usually through an environment variable (I think for NetApps it's HIST=Y, though your backup software should have a list of the proper variables to set.)
If the backup software doesn't keep track of the file indexes for each dump, you may have to just restore each dump starting from a level 0 in turn. I'm not 100% certain, but I believe there's an NDMP environment variable syntax for NetApp that supports "only restore data for this directory, not the entire filesystem".
With NDMP, you're basically telling the filer "Start a backup of this type, and send me the stream of data to put on a tape (or whatever)". The backup software generally can't interpret the NDMP data stream, but can capture state and index information if a) the filer sends it and b) if the backup software can deal with it.
When you're doing a restore, you tell the filer "Please restore this directory or file, here's the data stream you sent me earlier" and the filer has to sift through the stream to find the proper file or directory. (If the filer and backup software can handle directed restores, you can set DIRECT=Y when restoring and go directly to a point in the stream where the file in question begins; this requires HIST=Y having been set when the backup was taken, and for the backup software to understand the index data sent by the filer, again.)
Sorry if that's more than you wanted; NDMP can be a bit weird when looking at it from the perspective of normal server or workstation backups.
-dalvenjah
On Dec 20, 2011, at 2:59 PM, Ian Dotson wrote:
We've just started using our first Netapp here. One surprise involves backups (we're using NetVault's NDMP plugin). I'll let our local backup guy explain:
"We're setting up our new netapp, have the ndmp plugin in place and can back up ok. But I don't see how to set up backups of netapp filer volumes so that I can do restores in the same way we can do restores from windows file servers. Specifically, the ndmp restore window only shows the files backed up in that specific dump, so if I want to restore all files that existed in a directory up to that date, it appears I have to separately do a restore of the level 0 dump, then all pertinent level 1 dumps, then all pertinent level 2 dumps, etc. With windows file restores, I could restore the whole directory with one job. How do I set up the netapp ndmp to work like that? "
The NetVault folks reply that "the NDMP protocol doesn't allow for that. Each restore builds on the previous restore, so you have to do Level 0, Level 1, etc.. It would be the same with any filer that utilizes the NDMP protocol" -- which doesn't seem right at all.
So, is this indeed the same for those using NetBackup, etc.? Are you forced to restore each dump level individually?
Thanks, Ian Dotson _______________________________________________ Toasters mailing list Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters