I repeated cache drop/bench a few times and the results are
consistent but high: 1500-1600 IOPS
Vlad
On 9/7/22 07:58, Sridhar Seshasayee wrote:
Hi Vladimir,
Yes, device caching is disabled. The ODSs in question use a
separate DB/WAL device on flash. Could that be the cause of
IOPS over-estimation?
2000 IOPS definitely looks high for a HDD. The in-built osd
bench tool
writes to the backing device of the osd to determine the
IOPS capacity.
With DB/WAL configured, I wouldn't expect a wide variation.
To confirm the IOPS measurement, you can run the following
commands:
$ ceph tell osd.N cache drop
followed by,
$ ceph tell osd.N bench 12288000 4096 4194304 100
Where N is the osd id.
You can run the above sequence a few times to confirm if
there are any wide variations and
if so, it probably warrants more investigation into why
that's the case.
Also, may I know the following:
- what kind of HDDs are you using in your environment?
- Ceph version
Is it better for me to manually set
osd_mclock_max_capacity_iops_hdd to a reasonable number or
will things perform OK as long as IOPS are over-estimated
consistently everywhere?
I think it's better to figure out why the IOPS are on the
higher side first.
-Sridhar
<https://www.redhat.com>
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