Hi Dave,
On Jan 14, 2011, at 17:43 , Lewis, Dave wrote:
> I'm wondering what is a reasonable size for large AFS volumes. I
> understand that the maximum size of a volume is about 2 TB (assuming
> that the partition is at least that size). From a practical standpoint,
> is it reasonable to have a 2 TB volume? Should I expect any problems
> doing operations like bos salvage or vos move on large volumes?
we've been using a considerable number of volumes in the 100-500 GB range for a
while, without any problems we didn't experience with smaller volumes as well.
Moving them of course takes longer (although moving a 10 GB Volume with lots
and lots of files can take longer than moving a 100GB Volume with fewer files),
and it's harder to find a new home for them, and it will take longer to clean
up the mess if things go wrong. But it works fine in practice.
Our largest volume ever was some 900 GB. It was moved a few times, without
problems.
> For example, I'm wondering if bos salvage has a "harder" time with a few
> large volumes than with several smaller volumes.
It may need more temporary space, I think, but there'll be more elaborate
answers I guess.
> I figure that, with
> smaller volumes, internal inconsistencies that bos salvage fixes would
> be more isolated than with large volumes, and that that would be
> beneficial. But I don't really know.
From our experience, a volume can be a fault domain. You either get it online
after an incident (like hardware failure) or not. All of it. Yes, this is a
good reason to limit volume size to what is required.
> Currently we mount 25 GB volumes in users' home directories for their
> image data, which grows a lot during data processing. Some users are
> starting to feel limited by 25 GB volumes, so I'm considering going to
> 100 GB volumes. I would appreciate any advice. Should large volumes be
> salvaged more often than small volumes?
100 GB volumes work fine for us in practice. Even moving them is acceptably
fast with current hardware. Again, it depends on the number of files as well as
the total amount of data.
Looking forward to reading others' statements,
Stephan
--
Stephan Wiesand
DESY -DV-
Platanenenallee 6
15738 Zeuthen, Germany
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