Unexpected zfs ARC behavior
FF
fusionfoto at gmail.com
Sun Sep 28 09:00:52 UTC 2014
I'm not sure, but this may be addressed by :
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=191510.
On the same system, on a brand new SSD (Intel 320 series, supports TRIM,
973 hours of total run time and no SMARTCTL errors), the l2arc is accruing
some errors and I can't tell if they are inter-related or not.
sysctl -a |grep l2_
kstat.zfs.misc.arcstats.evict_l2_cached: 8717673244160
kstat.zfs.misc.arcstats.evict_l2_eligible: 2307662193664
kstat.zfs.misc.arcstats.evict_l2_ineligible: 3432677600768
kstat.zfs.misc.arcstats.l2_hits: 11990587
kstat.zfs.misc.arcstats.l2_misses: 66503164
kstat.zfs.misc.arcstats.l2_feeds: 3721611
kstat.zfs.misc.arcstats.l2_rw_clash: 153
kstat.zfs.misc.arcstats.l2_read_bytes: 1152794672128
kstat.zfs.misc.arcstats.l2_write_bytes: 27096209368064
kstat.zfs.misc.arcstats.l2_writes_sent: 1741090
kstat.zfs.misc.arcstats.l2_writes_done: 1741090
kstat.zfs.misc.arcstats.l2_writes_error: 0
kstat.zfs.misc.arcstats.l2_writes_hdr_miss: 2479
kstat.zfs.misc.arcstats.l2_evict_lock_retry: 1149
kstat.zfs.misc.arcstats.l2_evict_reading: 137
kstat.zfs.misc.arcstats.l2_free_on_write: 1000507
kstat.zfs.misc.arcstats.l2_abort_lowmem: 225
kstat.zfs.misc.arcstats.l2_cksum_bad: 8
kstat.zfs.misc.arcstats.l2_io_error: 6
kstat.zfs.misc.arcstats.l2_size: 35261600768
kstat.zfs.misc.arcstats.l2_asize: 33760987648
kstat.zfs.misc.arcstats.l2_hdr_size: 58288928
kstat.zfs.misc.arcstats.l2_compress_successes: 31952645
kstat.zfs.misc.arcstats.l2_compress_zeros: 903
kstat.zfs.misc.arcstats.l2_compress_failures: 436119
kstat.zfs.misc.arcstats.l2_write_trylock_fail: 2481253
kstat.zfs.misc.arcstats.l2_write_passed_headroom: 61954692
kstat.zfs.misc.arcstats.l2_write_spa_mismatch: 26664326
kstat.zfs.misc.arcstats.l2_write_in_l2: 19967700467
kstat.zfs.misc.arcstats.l2_write_io_in_progress: 94722
kstat.zfs.misc.arcstats.l2_write_not_cacheable: 11359575294
kstat.zfs.misc.arcstats.l2_write_full: 730445
kstat.zfs.misc.arcstats.l2_write_buffer_iter: 3721611
kstat.zfs.misc.arcstats.l2_write_pios: 1741090
kstat.zfs.misc.arcstats.l2_write_buffer_bytes_scanned: 3464594001047552
kstat.zfs.misc.arcstats.l2_write_buffer_list_iter: 229359623
kstat.zfs.misc.arcstats.l2_write_buffer_list_null_iter: 65007815
Anyway, thanks in advance for any help offered.
Best.
On Sat, Sep 27, 2014 at 2:24 PM, FF <fusionfoto at gmail.com> wrote:
>
> Hi, forwarding from -questions.
>
> It looks like the image didn't make it across, so here it is:
>
> http://snag.gy/Ghb7X.jpg
>
> Thanks in advance for any pointers or suggestions, or confirmations that
> somehow this behavior is normal.
>
> --
>
>
> So on a somewhat loaded ZFS file server (all NFS) serving mostly VMs with
> the load steadily increasing over the month (migrated from other
> servers)... the ARC size has unexpectedly dropped (please see attached
> graphic, if it makes through the mailing list server). The system peaks
> around 2,000 NFS IOPS and hasn't exhibited any slow downs. The L2ARC has a
> very low hit rate and prefetch has been turned off to increase the L2ARC
> efficiency... but none of that should really matter as far as I can tell
> since the L1ARC should try to use all the memory it can.
>
>>
>> Some tuning of zfs sysctls (mostly write_boost and write_max) to increase
>> them, but this has since been backed off to default.
>>
>> vmstat -m reports that 24G is dedicated to opensolaris:
>> solaris 1113433 24565820K - 6185559839
>> 16,32,64,128,256,512,1024,2048,4096
>>
>> And top reports memory free:
>>
>> last pid: 32075; load averages: 0.16, 0.13,
>> 0.14 up 36+21:44:59 09:16:49
>> 24 processes: 1 running, 23 sleeping
>> CPU: 0.0% user, 0.0% nice, 0.0% system, 0.6% interrupt, 99.4% idle
>> Mem: 25M Active, 1187M Inact, 26G Wired, 2048K Cache, 1536M Buf, 4160M
>> Free
>> ARC: 14G Total, 1679M MFU, 12G MRU, 28M Anon, 156M Header, 21M Other
>>
>> zfs-stats -a :
>>
>> ------------------------------------------------------------------------
>> ZFS Subsystem Report Sat Sep 27 09:17:07 2014
>> ------------------------------------------------------------------------
>>
>> System Information:
>>
>> Kernel Version: 902001 (osreldate)
>> Hardware Platform: amd64
>> Processor Architecture: amd64
>>
>> ZFS Storage pool Version: 5000
>> ZFS Filesystem Version: 5
>>
>> FreeBSD 9.2-RELEASE-p10 #0 r270148M: Mon Aug 18 23:14:36 EDT 2014 root
>> 9:17AM up 36 days, 21:45, 2 users, load averages: 0.12, 0.12, 0.13
>>
>> ------------------------------------------------------------------------
>>
>> System Memory:
>>
>> 0.08% 26.22 MiB Active, 3.75% 1.16 GiB Inact
>> 82.36% 25.47 GiB Wired, 0.01% 2.00 MiB Cache
>> 13.80% 4.27 GiB Free, 0.00% 1.03 MiB Gap
>>
>> Real Installed: 32.00 GiB
>> Real Available: 99.63% 31.88 GiB
>> Real Managed: 97.01% 30.93 GiB
>>
>> Logical Total: 32.00 GiB
>> Logical Used: 83.03% 26.57 GiB
>> Logical Free: 16.97% 5.43 GiB
>>
>> Kernel Memory: 23.54 GiB
>> Data: 99.90% 23.52 GiB
>> Text: 0.10% 23.13 MiB
>>
>> Kernel Memory Map: 29.76 GiB
>> Size: 76.40% 22.74 GiB
>> Free: 23.60% 7.02 GiB
>>
>> ------------------------------------------------------------------------
>>
>> ARC Summary: (HEALTHY)
>> Memory Throttle Count: 0
>>
>> ARC Misc:
>> Deleted: 90.09m
>> Recycle Misses: 2.44m
>> Mutex Misses: 794.67k
>> Evict Skips: 17.90m
>>
>> ARC Size: 44.78% 13.40 GiB
>> Target Size: (Adaptive) 44.78% 13.40 GiB
>> Min Size (Hard Limit): 12.50% 3.74 GiB
>> Max Size (High Water): 8:1 29.93 GiB
>>
>> ARC Size Breakdown:
>> Recently Used Cache Size: 86.16% 11.55 GiB
>> Frequently Used Cache Size: 13.84% 1.85 GiB
>>
>> ARC Hash Breakdown:
>> Elements Max: 786.71k
>> Elements Current: 87.05% 684.85k
>> Collisions: 153.35m
>> Chain Max: 16
>> Chains: 194.92k
>>
>> ------------------------------------------------------------------------
>>
>> ARC Efficiency: 506.24m
>> Cache Hit Ratio: 87.56% 443.25m
>> Cache Miss Ratio: 12.44% 62.99m
>> Actual Hit Ratio: 80.06% 405.29m
>>
>> Data Demand Efficiency: 93.92% 372.74m
>> Data Prefetch Efficiency: 49.49% 69.76m
>>
>> CACHE HITS BY CACHE LIST:
>> Anonymously Used: 6.10% 27.05m
>> Most Recently Used: 31.37% 139.05m
>> Most Frequently Used: 60.07% 266.24m
>> Most Recently Used Ghost: 0.80% 3.56m
>> Most Frequently Used Ghost: 1.66% 7.35m
>>
>> CACHE HITS BY DATA TYPE:
>> Demand Data: 78.98% 350.09m
>> Prefetch Data: 7.79% 34.53m
>> Demand Metadata: 12.15% 53.86m
>> Prefetch Metadata: 1.08% 4.77m
>>
>> CACHE MISSES BY DATA TYPE:
>> Demand Data: 35.95% 22.65m
>> Prefetch Data: 55.93% 35.23m
>> Demand Metadata: 4.49% 2.83m
>> Prefetch Metadata: 3.63% 2.29m
>>
>> ------------------------------------------------------------------------
>> <cut>
>>
>> Any suggestions? Is this expected or acceptable behavior?
>>
>> Thanks in advance,
>>
>> --
>> FF
>>
>
>
>
> --
> FF
>
--
FF
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