Hi all,
On our production system on r255173 we have problem with abnormal high system
load caused (not sure) with L2ARC placed on a few SSD, 490 GB total size.
After a fresh boot everything seems to be fine, Load Average less then 5.00.
But after some time (nearly day-two) Load Average jump to 10.. 20+ and system
goes really slow, IO opearations with zfs pool grows from ms to even seconds.
And L2ARC sysctls are pretty disturbing:
[frv:~]$ sysctl -a | grep l2
vfs.zfs.l2arc_write_max: 25000000
vfs.zfs.l2arc_write_boost: 50000000
vfs.zfs.l2arc_headroom: 8
vfs.zfs.l2arc_feed_secs: 1
vfs.zfs.l2arc_feed_min_ms: 30
vfs.zfs.l2arc_noprefetch: 0
vfs.zfs.l2arc_feed_again: 1
vfs.zfs.l2arc_norw: 1
vfs.zfs.l2c_only_size: 1525206040064
vfs.cache.numfullpathfail2: 4
kstat.zfs.misc.arcstats.evict_l2_cached: 6592742547456
kstat.zfs.misc.arcstats.evict_l2_eligible: 734016778752
kstat.zfs.misc.arcstats.evict_l2_ineligible: 29462561417216
kstat.zfs.misc.arcstats.l2_hits: 576550808
kstat.zfs.misc.arcstats.l2_misses: 128158998
kstat.zfs.misc.arcstats.l2_feeds: 1524059
kstat.zfs.misc.arcstats.l2_rw_clash: 1429740
kstat.zfs.misc.arcstats.l2_read_bytes: 2896069043200
kstat.zfs.misc.arcstats.l2_write_bytes: 2405022640128
kstat.zfs.misc.arcstats.l2_writes_sent: 826642
kstat.zfs.misc.arcstats.l2_writes_done: 826642
kstat.zfs.misc.arcstats.l2_writes_error: 0
kstat.zfs.misc.arcstats.l2_writes_hdr_miss: 1059415
kstat.zfs.misc.arcstats.l2_evict_lock_retry: 1640
kstat.zfs.misc.arcstats.l2_evict_reading: 0
kstat.zfs.misc.arcstats.l2_free_on_write: 8580680
kstat.zfs.misc.arcstats.l2_abort_lowmem: 2096
kstat.zfs.misc.arcstats.l2_cksum_bad: 212832715
kstat.zfs.misc.arcstats.l2_io_error: 5501886
kstat.zfs.misc.arcstats.l2_size: 1587962307584
kstat.zfs.misc.arcstats.l2_asize: 1425666718720
kstat.zfs.misc.arcstats.l2_hdr_size: 82346948208
kstat.zfs.misc.arcstats.l2_compress_successes: 41707766
kstat.zfs.misc.arcstats.l2_compress_zeros: 0
kstat.zfs.misc.arcstats.l2_compress_failures: 0
kstat.zfs.misc.arcstats.l2_write_trylock_fail: 8847701930
kstat.zfs.misc.arcstats.l2_write_passed_headroom: 21220076
kstat.zfs.misc.arcstats.l2_write_spa_mismatch: 27619372107
kstat.zfs.misc.arcstats.l2_write_in_l2: 418007172085
kstat.zfs.misc.arcstats.l2_write_io_in_progress: 29279
kstat.zfs.misc.arcstats.l2_write_not_cacheable: 131001473113
kstat.zfs.misc.arcstats.l2_write_full: 63699
kstat.zfs.misc.arcstats.l2_write_buffer_iter: 1524059
kstat.zfs.misc.arcstats.l2_write_pios: 826642
kstat.zfs.misc.arcstats.l2_write_buffer_bytes_scanned: 8433038008130560
kstat.zfs.misc.arcstats.l2_write_buffer_list_iter: 96529899
kstat.zfs.misc.arcstats.l2_write_buffer_list_null_iter: 9228464
Here is output from zfs-stats about L2:
[frv:~]$ zfs-stats -L
------------------------------------------------------------------------
ZFS Subsystem Report Mon Oct 7 20:50:19 2013
------------------------------------------------------------------------
L2 ARC Summary: (DEGRADED)
Passed Headroom: 21.22m
Tried Lock Failures: 8.85b
IO In Progress: 29.32k
Low Memory Aborts: 2.10k
Free on Write: 8.59m
Writes While Full: 63.71k
R/W Clashes: 1.43m
Bad Checksums: 213.07m
IO Errors: 5.51m
SPA Mismatch: 27.62b
L2 ARC Size: (Adaptive) 1.44 TiB
Header Size: 5.19% 76.70 GiB
L2 ARC Evicts:
Lock Retries: 1.64k
Upon Reading: 0
L2 ARC Breakdown: 705.25m
Hit Ratio: 81.82% 577.01m
Miss Ratio: 18.18% 128.24m
Feeds: 1.52m
L2 ARC Buffer:
Bytes Scanned: 7.49 PiB
Buffer Iterations: 1.52m
List Iterations: 96.55m
NULL List Iterations: 9.23m
L2 ARC Writes:
Writes Sent: 100.00% 826.96k
----------------------------------------------------------------------
In /boot/loader.conf (128GB RAM in system):
vm.kmem_size="110G"
vfs.zfs.arc_max="100G"
vfs.zfs.arc_min="80G"
vfs.zfs.vdev.cache.size=16M
vfs.zfs.vdev.cache.max="16384"
vfs.zfs.txg.timeout="10"
vfs.zfs.write_limit_min="134217728"
vfs.zfs.vdev.cache.bshift="14"
vfs.zfs.arc_meta_limit=53687091200
vfs.zfs.l2arc_write_max=25165824
vfs.zfs.l2arc_write_boost=50331648
vfs.zfs.l2arc_noprefetch=0
In /etc/sysctl.conf:
vfs.zfs.l2arc_write_max=25000000
vfs.zfs.l2arc_write_boost=50000000
vfs.zfs.l2arc_noprefetch=0
vfs.zfs.l2arc_headroom=8
vfs.zfs.l2arc_feed_min_ms=30
vfs.zfs.arc_meta_limit=53687091200
How can L2 ARC Size: (Adaptive) be 1.44 TiB (up) with total physical size of
L2ARC devices 490GB?
Why this values can grow and become so high?
kstat.zfs.misc.arcstats.l2_cksum_bad: 212832715
kstat.zfs.misc.arcstats.l2_io_error: 5501886
Thanks for any help and ideas!
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