n comp.unix.admin "Michael wrote:
This used to be an issue with us and SBU, but it's not anymore. When the
index format changed between versions 5.x and 6, the indexes shrank
quite a bit. I used to run nsrck regularly to reclaim space, but now it
stays at 100% used (i.e., no gaps in the data, a good thing). Usage in
the index filesystem dropped by close to 50% with the change.
You're right about the time - With ~90 clients, some with few and some
with many (xxx,xxx) files, it generally took us about 6 hours to check
them all. With the new format, it's much more efficient. In general,
we've been advised by Sun not to run index utilities as a maintenance
tool, but rather only as needed as a repair tool. These days, the
indexes pretty much take care of themselves. However, nsrck can be
interrupted without harm. In fact, until I upped the data size and file
handles limit with ulimit, it would regularly die about halfway through,
but without any damage.
SBU (Legato) has two levels of indexing (catalogs): The media index
contain what savesets (typically filesystems) are on what media and the
file index contains what files are in a given saveset. When the Browse
Policy is passed, the file indexes expire and its' no longer possible to
browse for files during a restore. However, you can still recover entire
filesystems and (I think) even a given file if you know the file's
location. When the Retention Policy is passed, nothing changes except
the saveset it considered Recyclable. When all savesets on a given media
pass the Retention Policy, that media is recyclable and will be
automatically reused if physically available. However, the media index
entry for that volume (tape) and saveset remain intact until the media
is relabeled (erased). To get the file index back for an expired volume,
you have to scan it in, which is generally about a 3-4 hour process for
a DLT7000 volume.
For simplicity, we generally set both policies to the same value.
I understand your point, but see above re: media index and scanning. The
data will stay on the tape and even if the indexes are deleted, scanning
it in will rebuild all that. Still, having backups on more than one
media never hurts. In fact, before I upgrade Solaris and Veritas Volume
Manager next week on our production server, I'll run backups on both DLT
and 8mm Mammoth tape.
-- Len Philpot ><> --
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