[OpenAFS] volume size

Stephan Wiesand stephan.wiesand@desy.de
Fri, 14 Jan 2011 18:11:16 +0100

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). =46rom a practical =
> 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 =
> 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.

=46rom 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 Wiesand
Platanenenallee 6
15738 Zeuthen, Germany