Hi Sridhar
Thanks for the information.
The above values are a result of distributing the IOPS across all the OSD
shards as defined by the
osd_op_num_shards_[hdd|ssd] option. For HDDs, this is set to 5 and
therefore the IOPS will be
distributed across the 5 shards (i.e. for e.g., 675/5 for
osd_mclock_scheduler_background_recovery_lim
and so on for other reservation and limit options).
Why was it done that way? I do not understand the reason why distributing the IOPS accross
different disks, when the measurement we have is for one disk alone. This means with
default parameters we will always be far from reaching OSD limit right?
Luis Domingues
Proton AG
------- Original Message -------
On Monday, April 3rd, 2023 at 07:43, Sridhar Seshasayee <sseshasa(a)redhat.com>
wrote:
> Hi Luis,
>
>
> I am reading reading some documentation about mClock and have two questions.
>
> > First, about the IOPS. Are those IOPS disk IOPS or other kind of IOPS? And
> > what the assumption of those? (Like block size, sequential or random
> > reads/writes)?
>
>
> This is the result of testing running OSD bench random writes at 4 KiB
> block size.
>
> > But what I get is:
> >
> > "osd_mclock_scheduler_background_best_effort_lim":
"999999",
> > "osd_mclock_scheduler_background_best_effort_res": "18",
> > "osd_mclock_scheduler_background_best_effort_wgt": "2",
> > "osd_mclock_scheduler_background_recovery_lim": "135",
> > "osd_mclock_scheduler_background_recovery_res": "36",
> > "osd_mclock_scheduler_background_recovery_wgt": "1",
> > "osd_mclock_scheduler_client_lim": "90",
> > "osd_mclock_scheduler_client_res": "36",
> > "osd_mclock_scheduler_client_wgt": "1",
> >
> > Which seems very low according to what my disk seems to be able to handle.
> >
> > Is this calculation the expected one? Or did I miss something on how those
> > profiles are populated?
>
The above values are a result of distributing the IOPS across all the OSD
shards as defined by the
osd_op_num_shards_[hdd|ssd] option. For HDDs, this is set to 5 and
therefore the IOPS will be
distributed across the 5 shards (i.e. for e.g., 675/5 for
osd_mclock_scheduler_background_recovery_lim
and so on for other reservation and limit options).
>
> -Sridhar
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