Date: Wed, 26 Mar 2014 11:52:46 -0400 From: Vick Khera <vivek@khera.org> To: freebsd-questions@freebsd.org Subject: ZFS l2arc stats not updating Message-ID: <CALd%2BdcfCcAg8wbu18dq851Gx=sd5jVfcMd68fmWWF7TkKHbbaw@mail.gmail.com>
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I have two identical FreeBSD 10.0/amd64 systems I recently put into
production running ZFS. They have 256GB of RAM each. I installed the
zfs-stats utility to monitor their stats. The zfs-mon program on one
of the boxes does not report any L2ARC stats, while the other one
does. Checking the stats via sysctl shows that
kstat.zfs.misc.arcstats.l2_misses and kstat.zfs.misc.arcstats.l2_hits
are not updating on the host for which zfs-mon shows no L2 data.
They are both configured identically via script-generated files. The
ZFS pool was created identically as well. The hardware was
manufactured at the same time. I can find nothing in sysctl output
that would indicate that the L2ARC is somehow disabled, and it does
indeed seem to be getting updated by the system when watching iostat
output.
Any clues where to look to see why my L2ARC stats are not updating on
just the one host? Both are doing a fair amount of read/write
activity.
Host A (the one not reporting L2 stats):
% zpool iostat -v
capacity operations bandwidth
pool alloc free read write read write
---------------- ----- ----- ----- ----- ----- -----
zfspool 57.6G 1.03T 7 246 112K 1.99M
mirror 28.8G 527G 3 123 56.0K 1018K
label/zdisk0 - - 0 59 31.0K 1019K
label/zdisk1 - - 0 59 31.0K 1019K
mirror 28.7G 527G 3 123 56.0K 1018K
label/zdisk2 - - 0 57 30.9K 1019K
label/zdisk3 - - 0 57 31.1K 1019K
cache - - - - - -
label/zcache0 93.1G 16.0M 0 8 0 689K
label/zcache1 93.1G 16M 0 8 0 688K
---------------- ----- ----- ----- ----- ----- -----
% zfs-mon -ALZ -b
ZFS real-time cache activity monitor
Cache efficiency percentage:
10s 60s tot
ARC: 100.00 100.00 100.00
ZFETCH: 48.44 48.44 48.44
% sysctl kstat.zfs.misc.arcstats.l2_misses
kstat.zfs.misc.arcstats.l2_misses: 4073823
% sysctl kstat.zfs.misc.arcstats.l2_hits
kstat.zfs.misc.arcstats.l2_hits: 0
these above values are not changing. However, watching the zpool
iostat values, the cache drives do get read/write activity and the
capacity numbers change.
Host B:
% zpool iostat -v
capacity operations bandwidth
pool alloc free read write read write
---------------- ----- ----- ----- ----- ----- -----
zfspool 130G 982G 101 313 1.23M 2.83M
mirror 64.8G 491G 50 156 632K 1.41M
label/zdisk0 - - 14 45 431K 1.41M
label/zdisk1 - - 14 45 431K 1.41M
mirror 64.8G 491G 50 156 632K 1.41M
label/zdisk2 - - 14 45 432K 1.41M
label/zdisk3 - - 14 45 433K 1.41M
cache - - - - - -
label/zcache0 93.1G 8M 1 4 18.4K 264K
label/zcache1 93.1G 7.98M 1 4 18.3K 265K
---------------- ----- ----- ----- ----- ----- -----
% zfs-mon -ALZ -b
ZFS real-time cache activity monitor
Cache efficiency percentage:
10s 60s tot
ARC: 100.00 100.00 100.00
L2ARC: 0.00 0.00 0.00
ZFETCH: 32.88 32.88 32.88
% sysctl kstat.zfs.misc.arcstats.l2_misses
kstat.zfs.misc.arcstats.l2_misses: 42635721
% sysctl kstat.zfs.misc.arcstats.l2_hits
kstat.zfs.misc.arcstats.l2_hits: 1605684
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