Well it is just the same as an ordinary backup, you have a file list and
you can restore any single files if you like.
The limitations with NDMP tend to be:
1. Performance - you are dealing with an appliance, so you cannot
tune the tape driver - the block size for a NetApp is 64k, and currently
you cannot change it. LTO drives perform better with a larger blocksize
than 64k, so you may not get what you pay for on the tape drives.
2. Restoring wildcards, including folders. Direct Access Restore
(DAR) is a scheme where the approximate location of a file on the tape is
recorded in the catalogue. It allows a restore to rapidly move a tape to
the right block, then read that block for the file(s). Without DAR the
whole backup is scanned for the file(s) - and of course as a wildcard may
match right up to the end, it reads all the tapes in the backup end to
end. This can take many hours, even if the files you actually want were
found in the first few minutes. NetApp do support DAR; by default only
if you specify explicit files to restore (and that as I say rules out
folders). This is tough on operators, if user X says "please restore my
folder", they don't know that because this particular restore is from an
NDMP backup, they should if possible select to restore all the files in
the folder individually, and not select the folder itself....
But, I see in the NetApp NDMP system options you can trun on "extended
DAR", which in conjunction with NetBackup telling the NetApp to use TAR
(not Dump), will support restores of folders. I've not tried it, because
I'm not sure that if you use TAR you don't lose the Windows ACLs. The
reason to use NDMP is usually that you have both CIFS and NFS permissions
on files, and the only way to preserve these is to use Dump.
I think using NDMP is just right for you, we use it. But consider, you
would then not be backing up anything on the client - the OS, the
configuration, the files the user put there even though you told them not
to....
William D L Brown
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