On 8/9/22 4:07 PM, Robert Sander wrote:
Hi,
we have a cluster with 7 nodes each with 10 SSD OSDs providing CephFS
to a CloudStack system as primary storage.
When copying a large file into the root directory of the CephFS the
bandwidth drops from 500MB/s to 50MB/s after around 30 seconds. We see
some MDS activity in the output of "ceph fs status" at the same time.
When copying the same file to a subdirectory of the CephFS the
performance stays at 500MB/s for the whole time. MDS activity does not
seems to influence the performance here.
There are appr 270 other files in the root directory. CloudStack
stores VM images in qcow2 format there.
Is this a known issue?
Is there something special with the root directory of a CephFS wrt
write performance?
AFAIK there is no special with the root dir. From my local test there is
not difference with the subdir.
BTW, could you test it for more than once for the root dir ? When you
are doing this for the first time the ceph may need to allocate the disk
spaces, which will take a little time.
Thanks.
Regards
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