[BBLISA] ZFS question

[Theo Van Dinter]

On Thu, Oct 25, 2007 at 08:05:09PM -0400, Tom Metro wrote:
> >One thought of how to with this was to simply tack on some generic
> >percentage to the quota, say 20%, which would allow for snapshots,
> >ie: 12G. 
> 
> This sounds more like a matter of perspective than a technical problem. 
> If the point to using quotas is to limit per-user resource usage, then 
> it seems pretty reasonable to include snapshots in the quota. Make the 
> user aware of this, and seeing as you are customizing thing per user, 
> give them the choice of how much space should be used up by snapshots 
> (indirectly by tuning the frequency of the snapshots).

Ok, that's a fair point, and user education is a possible way to deal
with it.  It's also an acceptable thing to do in certain situations
where you would want to totally limit the usage.

Homedirs and (in my experience) most file shares don't fall in that
category though.  When people are told they have 10G, they expect to
always be able to write 10G to the active filesystem.  I don't like
situations where usesr can't write any data to their dir and have to
call me to fix it.  ;)

While poking about, I ran across
http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6431277 which
is exactly the same issue. :)   Apparently in b76 there's a new "refquota"
property which does what I wanted.  It sets a "quota" on the filesystem,
but does not include descendents such as snapshots.  You can also set the
standard "quota" property which still limits the full usage as before, so that
would give a reserved space for just snapshots.

So this issue may have become moot.  I've been using b72, and apparently the
latest version I can download is b75...  /me waits

> Does ZFS support soft quota limits? That would be one way of alerting 
> the user that they are going beyond the limits where they will be able 
> to maintain both data and snapshots.

No, it's just hard quota limits.  And by quota, it's really "filesystem size"
and not a quota.  I don't like that they hijacked the term.

-- 
Theo Van Dinter
Systems Administrator: bblisa.org, kluge.net, google.com, etc.
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