[ceph-users] question pool usage vs. pool usage raw

bernhard.glomm bernhard.glomm at ecologic.eu
Thu Nov 23 06:59:30 PST 2017


this question has probably come up before but I couldn't find any clear 
answer so far.

What is the difference between the "usage" and the "raw usage" of a 
pool?

We are using only rbds (no rados no cephfs as for now)
On the first glance the "sum of all rbd sizes" equals the "usage". 
Right?
(rbs size as give by 'rbd ls -l <poolname> | egrep -v <any_snapshot>')
Even though the rbds are far from beeing filled with data, i.e.


Is the "raw usage" the "usage" + "space needed by all snapshots" (plus 
some overhead) in the pool?
(which unfortunately is NOT the sum of all 'rbd ls -l <poolname>')

Than the size of the pool would be "raw usage"+"available space"? Right?

In the results of "rados df" or "ceph df" the sum of usage per pool is - 
at the moment - less than 50% of the global usage.
And the global size of the cluster doesn't help me at all, since some 
pools are smaller, more expensive and much slower filling than others,
so I would trigger a notification on a much higher mark than on a huge 
cheap pool.
But I can't find a reliable way to figure out the size of a given pool 
(other than "usage + availabel", or is it "raw usage + available"?)

TIA

Bernhard


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