[OpenAFS] Volumes and disk partitions

[Esther Filderman]

On Thu, Jan 29, 2009 at 11:01 AM, David Miguel
<davidbranquinho@gmail.com> wrote:
> Hello,
>
> I have some questions concerning afs volumes and disk partitions:
>
> 1. An afs volume "is" a disk partition? Or a disk partition "has" afs
> volumes?

A disk partition is a section of disk on the AFS server which stores
AFS volumes.

Because of the nature of AFS, you cannot (generally) examine the
contents of an AFS volume on the local server disk,  it requires an
AFS client.

> 2. All afs volumes must have the same size?

AFS volumes can be any size, with an upper limit of around 4.something
Tb, if I recall correctly.  (I'm sure everyone will now correct me.)

However, larger volumes have an adminstrative overhead -- they take
longer to move, and to backup and restore.  Most folks, I think, seem
to try to cap volume sizes around 100-200G.

> 3. If a partition "has" an afs volume, can I have many volumes in a
> partition?

I'm not sure anyone's ever found an upper limit.  That said, again,
you want to think of administration.  Too many volumes + their backup
volumes can make an administrative headache.  That said, I've seen
cells with 10,000 volumes in a partition or more, on servers with
multiple partitions.

> 4. If a partition "is" a volume, it has to be the exact size of the volume?

It's not.

> 5. Is there any text with this topics, and/or advice on the optimal afs
> volume size?

See above.

You learn not to let volumes get too huge, and the opposite: Sometimes
there's no need for a zillion volumes.   You learn to step back and
say, "If I need to move/change/re-distribute this information, would
it be easier in it's own volume or can it share space with other
things?"

That said, always give your users their own volumes. :)