Last week I decided to take a look at the 'osd pool set-quota' option.
I have a directory in cephFS that uses a pool called pool-2 (configured by
following this:
http://www.sebastien-han.fr/blog/2013/02/11/mount-a-specific-pool-with-cephfs/).
I have a directory in that filled with cat pictures. I ran 'rados df'. I
then copied a couple more cat pictures into my directory using 'cp file
destination && sync'. I then ran 'rados df' again, this showed an increase in
the object count for the pool equal to the number of additional cat pictures
and an increase in the pool size equal to the size of the cat pictures, as
expected.
I then used the command 'ceph osd pool set-quota {pool-name} [max_objects
{obj-count}] [max_bytes {bytes}]', as per
http://ceph.com/docs/master/rados/operations/pools/, and set an object limit a
couple of objects bigger than the current pool size. I then ran a loop copying
more cat pictures one at a time (again with '&& sync') each time. Whilst doing
this I ran 'rados df', the number of objects in the pool increased up to the
limit and stopped. However on the machine copying the cat pictures, the copying
appeared to work fine and running ls showed more pictures than the 'rados df'
command would suggest should be there. If I accessed the same directory from a
different machine, then I saw only the pictures that were copied up to the
limit. If I then removed the limit, the images would appear in the directory
and 'rados df' would report a larger number of objects. Similar behaviour was
observed when setting a size limit. What's going on? Is this expected
behaviour?
George Ryall
Scientific Computing | STFC Rutherford Appleton Laboratory | Harwell Oxford |
Didcot | OX11 0QX
(01235 44) 5021
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