> - what kind of HDDs are you using in your environment?
Sorry, forgot to provide this. We use 9TB SAS, 12TB SAS
(JBOD mode, no write cache), 18TB SATA.
All drives report 1000-2500 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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