Hi Harald,
Your cluster has a lot of objects per osd/pg and the pg logs will grow
fast and large because of this. The pg_logs will keep growing as long as
you're clusters pgs are not active+clean. This means you are now in a
loop where you cannot get stable running OSDs because the pg_logs take
too much memory, and therefore the OSDs cannot purge the pg_logs...
I suggest you lower the values for both the osd_min_pg_log_entries and
the osd_max_pg_log_entries. Lowering these values will cause Ceph to go
into backfilling much earlier, but the memory usage of the OSDs will go
down significantly enabling them to run stable. The default is 3000 for
both of these values.
You can lower them to 500 by executing:
ceph config set osd osd_min_pg_log_entries 500
ceph config set osd osd_max_pg_log_entries 500
When you lower these values, you will get more backfilling instead of
recoveries but I think it will help you get through this situation.
kind regards,
Wout
42on
On 13-05-2020 07:27, Harald Staub wrote:
Hi Mark
Thank you for your feedback!
The maximum number of PGs per OSD is only 123. But we have PGs with a
lot of objects. For RGW, there is an EC pool 8+3 with 1024 PGs with
900M objects, maybe this is the problematic part. The OSDs are 510
hdd, 32 ssd.
Not sure, do you suggest to use something like
ceph-objectstore-tool --op trim-pg-log ?
When done correctly, would the risk be a lot of backfilling? Or also
data loss?
Also, to get up the cluster is one thing, to keep it running seems to
be a real challenge right now (OOM killer) ...
Cheers
Harry
On 13.05.20 07:10, Mark Nelson wrote:
Hi Herald,
Changing the bluestore cache settings will have no effect at all on
pglog memory consumption. You can try either reducing the number of
PGs (you might want to check and see how many PGs you have and
specifically how many PGs on that OSD), or decrease the number of
pglog entries per PG. Keep in mind that fewer PG log entries may
impact recovery. FWIW, 8.5GB of memory usage for pglog implies that
you have a lot of PGs per OSD, so that's probably the first place to
look.
Good luck!
Mark
On 5/12/20 5:10 PM, Harald Staub wrote:
Several OSDs of one of our clusters are down currently because RAM
usage has increased during the last days. Now it is more than we can
handle on some systems. Frequently OSDs get killed by the OOM
killer. Looking at "ceph daemon osd.$OSD_ID dump_mempools", it shows
that nearly all (about 8.5 GB) is taken by osd_pglog, e.g.
"osd_pglog": {
"items": 461859,
"bytes": 8445595868
},
We tried to reduce it, with "osd memory target" and even with
"bluestore cache autotune = false" (together with "bluestore cache
size hdd"), but there was no effect at all.
I remember the pglog_hardlimit parameter, but that is already set by
default with Nautilus I read. I.e. this is on Nautilus, 14.2.8.
Is there a way to limit this pglog memory?
Cheers
Harry
_______________________________________________
ceph-users mailing list -- ceph-users@xxxxxxx
To unsubscribe send an email to ceph-users-leave@xxxxxxx
_______________________________________________
ceph-users mailing list -- ceph-users@xxxxxxx
To unsubscribe send an email to ceph-users-leave@xxxxxxx
_______________________________________________
ceph-users mailing list -- ceph-users@xxxxxxx
To unsubscribe send an email to ceph-users-leave@xxxxxxx
_______________________________________________
ceph-users mailing list -- ceph-users@xxxxxxx
To unsubscribe send an email to ceph-users-leave@xxxxxxx
