-How does an "online" image backup work exactly in regards to open files?
According to the docs, "Corruption of the backup may occur if applications
write to the volume while the backup is in progress. In this case, run fsck
after a restore." So say this occurs.. What do you end up with backed up in
the case of that file that was written during the backup? The before version
or the after version? Or some hybrid fuzzy file after the restore? I don't
entirely see what good running fsck is going to be on a file that the bytes
changed in the middle of backing it up. Isn't the image just backing up at
the bit level and doesn't really pay attention to open files or changing
bytes? I guess I'd just like to hear more info on how an "online" image
backup would work.
-under "offline and online image backup" it also says "For linux86 only: TSM
performs an online image backup of file systems residing on a logical volume
created by the linux logical volume manager during which the volume is
available to other system applications". Can I infer that if I am just using
reiserfs that I cannot then do an online image backup - only an offline via
the device itself?
-I find it interesting that you can do an incremental image backup and not
entirely sure how that works either. Isn't an image backup just backing up
the filesystem bit by bit? How does it know which bits changed or which
files? If I read this correctly, it only works with lvm's. It says "Two
types of backup only apply to logical volumes: mode=selective (the default)
and mode=incremental.". So in the case of linux, if you're using reiserfs
I'm guessing you can't do an incremental image backup. You'd have to use
ext3 or something similar.
Gerald Wichmann
Senior Systems Development Engineer
Zantaz, Inc.
925.598.3099 (w)
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