Hello Surabh, you've got the right ideas already - collecting the
recovery/client stats from perf dump on each OSD is the most accurate
instantaneous measure.
The stats reported by ceph -s are aggregated from all osds, but have
some delay as the OSD sends updates to the mgr only overy 5 seconds by
default (mgr_stats_period controls this).
Depending on what you're trying to measure, the aggregated values in
ceph -s may be easier to use - that's what Sridhar used in testing
mclock QoS for example [0].
Josh
[0] https://docs.ceph.com/en/latest/dev/osd_internals/mclock_wpq_cmp_study/
On 7/19/21 9:26 AM, Surabhi GUPTA wrote:
Hi,
I am a graduate student at the university of wisconsin, Madison. I have
been trying to understand the recovery mechanisms in ceph and had a
question about accurate collection of metrics. My previous email might
have missed your notice, so sending a note again.
Any help regarding this would be highly appreciated.
Thank You,
Surabhi Gupta
Get Outlook for iOS <https://aka.ms/o0ukef>
------------------------------------------------------------------------
*From:* Surabhi GUPTA
*Sent:* Wednesday, July 14, 2021 5:47:47 PM
*To:* dev@xxxxxxx <dev@xxxxxxx>
*Subject:* Seeking advice regarding collecting better client and
recovery throughput metrics
Hi,
I was running some experiments to measure client IO throughput and
recovery throughput in a ceph cluster. I am a bit uncertain if I am
collecting the metrics correctly. Could you please tell me if this is
the right way or if I can do anything better to collect more accurate
statistics?
To generate load on the cluster, I use the rados bench utility and plot
the avg MB/s and cur MB/s values reported by the tool. For recovery, I
am periodically querying the perf dump for each osd and looking at the
recovery_ops and recovery_bytes. I then calculate the recovery
throughput based on the difference in values obtained on successive
querying and time difference between these queries.
I also saw that ceph health displays client iops and recovery iops. So
one way is to periodically query "ceph -s", extract these values and use
them for the analysis.
Could you please tell me which is the best way to obtain these metrics -
In the sense that which one exposes more accurate instantaneous
throughput values?
Is there any other method apart from these two that I should be looking at?
I would greatly appreciate any help regarding this!
Thank You,
Surabhi Gupta
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