[OpenAFS] Definitive list of AFS Limits?

Dan Pritts danno@internet2.edu
Thu, 21 Jul 2005 12:08:57 -0400

On Thu, Jul 21, 2005 at 12:16:49AM -0500, Christopher Mason wrote:
> Minimum file size (overhead): FAQ says 1k file occupies 1k, but 
> doesn't address overhead.

Others mentioned this but just so it's entirely clear, the file's size
on disk is dependent on the underlying filesystem used on the server,
whatever its limits on block size, etc.  If you were running linux and
had lots and lots of small files and cared more about space utilization
than best possible i/o speed, you might want to use reiserfs with tail
packing turned on.

> Maximum size of a partition:
> (OS limited? -- linux = 9TB?)

Linux with 2.6 kernels and the appropriate devices can support very
large filesystems.  I've got one filesystem that is ~11TB and if i recall
correctly the actual limit is much larger.  That said, this was pretty
bleeding edge when i set it up a few months ago, i ran into problems
with RAID firmware, fibre channel card's linux driver, and the linux LVM.

I should add that this system is *not* an AFS server, i'm talking only
about linux partition & filesystem sizes.

> Total size of largest known AFS installation:

As others have mentioned it's hard to say what exactly constitutes 
the largest installation.

I don't know raw numbers but AFS is in use at some large universities.
umich has about 38,000 students, and at least 10,000 faculty & staff.
Each of those people qualifies for an AFS home directory as part of a
basic computing offering.  I don't know how many of them actually use
one, or how many terabytes of disk they have online, but it's pretty
darn big.

Depending on the application you are looking at, you should be careful
that AFS meets your performance needs.  AFS is really good at being
distributed and scalable and secure.  It's not as good at being super

dan pritts - systems administrator - internet2
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