Hi,

Thanks a lot for the information.

I have a last question. Why is the bench performed using writes of 4 KiB. Is 
any reason to choose that over another another value?

On my lab, I tested with various values, and I have mainly two type of disks. 
Some Seagates and Toshiba.

If I do bench with 4KiB, what I get from Seagate is a result around 2000 IOPS. 
While the Toshiba is more arround 600.

If I do bench with 128KiB, I still have results arround 2000 IOPS for Seagate, 
but Toshiba also bench arround 2000 IOPS. And from the rados experiment I did, 
having osd_mclock_max_capacity_iops_hdd set to 2000 on that lab setup is the 
value I get the most performance from my rados experiments, both with Segate 
and Toshiba disks.

Luis Domingues
Proton AG


------- Original Message -------
On Monday, April 3rd, 2023 at 08:44, Sridhar Seshasayee <ssesh...@redhat.com> 
wrote:


> 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?
> > 
> > It's not on different disks. We distribute the IOPS across shards on a
> 
> given OSD/disk. This is an internal implementation detail.
> This means in your case, 450 IOPS is distributed across 5 shards on the
> same OSD/disk. You can think of it as 5 threads
> being allocated a share of the total IOPS on a given OSD.
> -Sridhar
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