Hi,
That's interesting -- yes on a lightly loaded cluster the metadata IO
should be almost nil.
You can debug what is happening using ceph daemonperf on the active
MDS, e.g.
https://pastebin.com/raw/n0iD8zXY
(Use a wide terminal to show all the columns).
Normally, lots of md io would indicate that the cache size is too
small for the workload; but since you said the clients are pretty
idle, this might not be the case for you.
Cheers, Dan
On Thu, Jul 8, 2021 at 9:36 AM Flemming Frandsen <dren.dk(a)gmail.com> wrote:
>
> We have a nautilus cluster where any metadata write operation is very slow.
>
> We're seeing very light load from clients, as reported by dumping ops in
> flight, often it's zero.
>
> We're also seeing about 100 MB/s writes to the metadata pool, constantly,
> for weeks on end, which seems excessive, as only 22GB is utilized.
>
> Should the writes to the metadata pool not quiet down when there's nothing
> going on?
>
> Is there any way i can get information about why the MDSes are thrashing so
> badly?
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