Hi. We're running OmniOS as a ZFS storage server. For some reason, our
arc cache will grow to a certain point, then suddenly drops. I used
arcstat to catch it in action, but I was not able to capture what else
was going on in the system at the time. I'll do that next.
read hits miss hit% l2read l2hits l2miss l2hit% arcsz l2size
166 166 0 100 0 0 0 0 85G 225G
5.9K 5.9K 0 100 0 0 0 0 85G 225G
755 715 40 94 40 0 40 0 84G 225G
17K 17K 0 100 0 0 0 0 67G 225G
409 395 14 96 14 0 14 0 49G 225G
388 364 24 93 24 0 24 0 41G 225G
37K 37K 20 99 20 6 14 30 40G 225G
For reference, it's a 12TB pool with 512GB SSD L2 ARC and 198GB RAM.
We have nothing else running on the system except NFS. We are also not
using dedupe. Here is the output of memstat at one point:
# echo ::memstat | mdb -k
Page Summary Pages MB %Tot
------------ ---------------- ---------------- ----
Kernel 19061902 74460 38%
ZFS File Data 28237282 110301 56%
Anon 43112 168 0%
Exec and libs 1522 5 0%
Page cache 13509 52 0%
Free (cachelist) 6366 24 0%
Free (freelist) 2958527 11556 6%
Total 50322220 196571
Physical 50322219 196571
According to "prstat -s rss" nothing else is consuming the memory.
592 root 33M 26M sleep 59 0 0:00:33 0.0% fmd/27
12 root 13M 11M sleep 59 0 0:00:08 0.0% svc.configd/21
641 root 12M 11M sleep 59 0 0:04:48 0.0% snmpd/1
10 root 14M 10M sleep 59 0 0:00:03 0.0% svc.startd/16
342 root 12M 9084K sleep 59 0 0:00:15 0.0% hald/5
321 root 14M 8652K sleep 59 0 0:03:00 0.0% nscd/52
So far I can't figure out what could be causing this. The only other
thing I can think of is that we have a bunch of zfs send/receive
operations going on as backups across 10 datasets in the pool. I am
not sure how snapshots and send/receive affect the arc. Does anyone
else have any ideas?
Thanks,
Chris
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