[OpenAFS] OpenAFS Quotas

[Esther Filderman]

On Thu, Oct 23, 2008 at 8:05 PM, Loren M. Lang <lorenl@north-winds.org> wrote:
> I have a dedicated partition for my OpenAFS server mounted at /vicepa
> and several volumes on it.  Do I need to make sure that the total of all
> the quotas on all my volumes do not exceed my partition size or does
> OpenAFS handle a full partition without causing corruption to volumes.

Some people do this to ease the management of their cell.  Some people
do load balancing, whether automagically (via 3rd party tools) or by
hand, when partitions start to get full.

That said, when a partition on a server gets full, moving volumes off
of it becomes a minor nightmare.  Generally to make a clean move, you
need to be able to make a copy, and without that room, the move can't
happen.  (To make a move, it's basically done by locking the volume,
making a copy, releasing the lock [so the user sees little "down"
time], dumping the copy to the new location, re-locking the volume,
doing an incremental copy [if needed] and unlocking and dumping that,
then bringing the new volume online & telling things that the location
of the volume has changed.)

However, I understand there's now a "-live" switch that lets you move
a volume without making a copy, but that means that the volume is
locked the whole time, so no changes can happen. This means more
downtime for the user.

> Also, how do quotas affect read-only and backup volumes on the same
> partition, does the read-only volume inherit it's quota from the RW
> volume possibly doubling the space requirements in case the RW version
> changes significantly before the next release?

*local* RO and backup volumes on the same partition (as opposed ro
read-only copies on other servers) should not completely double the
space used, as they share some ... um.   yeah, brain freeze here,
sorry.  Anyway.  They're not literal clones, so they don't use up the
same literal amount of space.

However, the perceived quota is the same.  If the RW is set to 5G of
space, the RO and the backup volume appear to be 5G of space.  Only a
RO copy on another site will truly use that 5G.

(How big will the local copy actually be?  That depends on a variety
of things including, most importantly, what has changed since the
clone was created.)

[...]
> this point I can't even create files which is expected.  Maybe I am just
> hitting a quirk with such a small quota, but I am just concerned that
> data is being lost unnecessarily when I hit the quota.

In the early days of AFS there was a bug where you would go to move a
file into a new volume, the volume would fill up, and it would unlink
(delete) the original before going, "Hey, there's no room!" and giving
you a 0 length file.

This was quickly fixed so if you move a file to a volume and fill up
the volume, yes, you may get a 0 length file at the new site, but the
old file isn't deleted.

moose