Fwd: Re: Strange ZFS performance

Jeremy Chadwick freebsd at jdc.parodius.com
Mon Apr 5 07:31:02 UTC 2010 

I'm not sure why this mail didn't make it to the mailing list (I do see
it CC'd).  The attachments are included inline.

SMART stats for the disk look fine, so the disk is unlikely to be
responsible for this issue.  OP, could you also please provide the
output of "atacontrol cap ad12"?

The arcstats entry that interested me the most was this (prior to the
reboot):

> kstat.zfs.misc.arcstats.memory_throttle_count: 39958287

The box probably needs tuning in /boot/loader.conf to relieve this
problem.

Below are values I've been using on our production systems for a month
or two now.  These are for machines with 8GB RAM installed.  The OP may
need to adjust the first two parameters (I tend to go with RAM/2 for
vm.kmem_size and then subtract a bit more for arc_max (in this case
512MB less than kmem_size)).

# Increase vm.kmem_size to allow for ZFS ARC to utilise more memory.
vm.kmem_size="4096M"
vfs.zfs.arc_max="3584M"

# Disable ZFS prefetching
# http://southbrain.com/south/2008/04/the-nightmare-comes-slowly-zfs.html
# Increases overall speed of ZFS, but when disk flushing/writes occur,
# system is less responsive (due to extreme disk I/O).
# NOTE: 8.0-RC1 disables this by default on systems <= 4GB RAM anyway
# NOTE: System has 8GB of RAM, so prefetch would be enabled by default.
vfs.zfs.prefetch_disable="1"

# Decrease ZFS txg timeout value from 30 (default) to 5 seconds.  This
# should increase throughput and decrease the "bursty" stalls that
# happen during immense I/O with ZFS.
# http://lists.freebsd.org/pipermail/freebsd-fs/2009-December/007343.html
# http://lists.freebsd.org/pipermail/freebsd-fs/2009-December/007355.html
vfs.zfs.txg.timeout="5"

-- 
| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

----- Forwarded message from Mikle <nekoexmachina at gmail.com> -----

> From: Mikle <nekoexmachina at gmail.com>
> To: Jeremy Chadwick <freebsd at jdc.parodius.com>
> Date: Mon, 5 Apr 2010 01:25:36 +0400
> Cc: freebsd-fs at freebsd.org
> Subject: Re: Strange ZFS performance
> 
> On Sun, Apr 04, 2010 at 01:41:27PM -0700, Jeremy Chadwick wrote:
> > Please provide the following output:
> > 
> > 1) uname -a
> > 2) sysctl kstat.zfs.misc.arcstats
> > 3) smartctl -a /dev/ad12
> FreeBSD takino.zet 8.0-STABLE FreeBSD 8.0-STABLE #0: Mon Mar  8 06:25:34 MSK 2010     root at takino.zet:/usr/obj/usr/src/sys/TAKINO  amd64
> (TAKINO is pretty basic untuned config, generic config plus ipfw-related things minus '-g' debug flag)
> sysctl & smart outputs are in the attaches.
> > Also, does rebooting the box restore write speed (yes, this is a serious
> > question/recommendation)?
> Yes, it did slightly: after reboot i got 6MB/s.
> 
> Also, one more (may be) related thing: there was a power-crash some time ago.   
> 
> Wbr,

> smartctl 5.39.1 2010-01-28 r3054 [FreeBSD 8.0-STABLE amd64] (local build)
> Copyright (C) 2002-10 by Bruce Allen, http://smartmontools.sourceforge.net
> 
> === START OF INFORMATION SECTION ===
> Model Family:     Western Digital Caviar Green family
> Device Model:     WDC WD10EADS-00M2B0
> Serial Number:    WD-WMAV50024981
> Firmware Version: 01.00A01
> User Capacity:    1,000,204,886,016 bytes
> Device is:        In smartctl database [for details use: -P show]
> ATA Version is:   8
> ATA Standard is:  Exact ATA specification draft version not indicated
> Local Time is:    Mon Apr  5 00:53:13 2010 MSD
> SMART support is: Available - device has SMART capability.
> SMART support is: Enabled
> 
> === START OF READ SMART DATA SECTION ===
> SMART overall-health self-assessment test result: PASSED
> 
> General SMART Values:
> Offline data collection status:  (0x84)	Offline data collection activity
> 					was suspended by an interrupting command from host.
> 					Auto Offline Data Collection: Enabled.
> Self-test execution status:      (   0)	The previous self-test routine completed
> 					without error or no self-test has ever 
> 					been run.
> Total time to complete Offline 
> data collection: 		 (19980) seconds.
> Offline data collection
> capabilities: 			 (0x7b) SMART execute Offline immediate.
> 					Auto Offline data collection on/off support.
> 					Suspend Offline collection upon new
> 					command.
> 					Offline surface scan supported.
> 					Self-test supported.
> 					Conveyance Self-test supported.
> 					Selective Self-test supported.
> SMART capabilities:            (0x0003)	Saves SMART data before entering
> 					power-saving mode.
> 					Supports SMART auto save timer.
> Error logging capability:        (0x01)	Error logging supported.
> 					General Purpose Logging supported.
> Short self-test routine 
> recommended polling time: 	 (   2) minutes.
> Extended self-test routine
> recommended polling time: 	 ( 230) minutes.
> Conveyance self-test routine
> recommended polling time: 	 (   5) minutes.
> SCT capabilities: 	       (0x303f)	SCT Status supported.
> 					SCT Feature Control supported.
> 					SCT Data Table supported.
> 
> SMART Attributes Data Structure revision number: 16
> Vendor Specific SMART Attributes with Thresholds:
> ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
>   1 Raw_Read_Error_Rate     0x002f   200   200   051    Pre-fail  Always       -       1
>   3 Spin_Up_Time            0x0027   111   107   021    Pre-fail  Always       -       7441
>   4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       488
>   5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
>   7 Seek_Error_Rate         0x002e   200   200   000    Old_age   Always       -       3
>   9 Power_On_Hours          0x0032   093   093   000    Old_age   Always       -       5568
>  10 Spin_Retry_Count        0x0032   100   100   000    Old_age   Always       -       0
>  11 Calibration_Retry_Count 0x0032   100   100   000    Old_age   Always       -       0
>  12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       290
> 192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       23
> 193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       464
> 194 Temperature_Celsius     0x0022   114   098   000    Old_age   Always       -       33
> 196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
> 197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
> 198 Offline_Uncorrectable   0x0030   200   200   000    Old_age   Offline      -       0
> 199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       1
> 200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       0
> 
> SMART Error Log Version: 1
> No Errors Logged
> 
> SMART Self-test log structure revision number 1
> No self-tests have been logged.  [To run self-tests, use: smartctl -t]
> 
> 
> SMART Selective self-test log data structure revision number 1
>  SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
>     1        0        0  Not_testing
>     2        0        0  Not_testing
>     3        0        0  Not_testing
>     4        0        0  Not_testing
>     5        0        0  Not_testing
> Selective self-test flags (0x0):
>   After scanning selected spans, do NOT read-scan remainder of disk.
> If Selective self-test is pending on power-up, resume after 0 minute delay.
> 

> kstat.zfs.misc.arcstats.hits: 10478566
> kstat.zfs.misc.arcstats.misses: 2896913
> kstat.zfs.misc.arcstats.demand_data_hits: 7189095
> kstat.zfs.misc.arcstats.demand_data_misses: 2588712
> kstat.zfs.misc.arcstats.demand_metadata_hits: 3289471
> kstat.zfs.misc.arcstats.demand_metadata_misses: 308201
> kstat.zfs.misc.arcstats.prefetch_data_hits: 0
> kstat.zfs.misc.arcstats.prefetch_data_misses: 0
> kstat.zfs.misc.arcstats.prefetch_metadata_hits: 0
> kstat.zfs.misc.arcstats.prefetch_metadata_misses: 0
> kstat.zfs.misc.arcstats.mru_hits: 4075848
> kstat.zfs.misc.arcstats.mru_ghost_hits: 184856
> kstat.zfs.misc.arcstats.mfu_hits: 6402718
> kstat.zfs.misc.arcstats.mfu_ghost_hits: 59708
> kstat.zfs.misc.arcstats.deleted: 2809459
> kstat.zfs.misc.arcstats.recycle_miss: 2950531
> kstat.zfs.misc.arcstats.mutex_miss: 3149
> kstat.zfs.misc.arcstats.evict_skip: 34090903
> kstat.zfs.misc.arcstats.hash_elements: 12170
> kstat.zfs.misc.arcstats.hash_elements_max: 20747
> kstat.zfs.misc.arcstats.hash_collisions: 363681
> kstat.zfs.misc.arcstats.hash_chains: 1727
> kstat.zfs.misc.arcstats.hash_chain_max: 5
> kstat.zfs.misc.arcstats.p: 344023154
> kstat.zfs.misc.arcstats.c: 414288960
> kstat.zfs.misc.arcstats.c_min: 53456640
> kstat.zfs.misc.arcstats.c_max: 427653120
> kstat.zfs.misc.arcstats.size: 409855944
> kstat.zfs.misc.arcstats.hdr_size: 2531984
> kstat.zfs.misc.arcstats.l2_hits: 0
> kstat.zfs.misc.arcstats.l2_misses: 0
> kstat.zfs.misc.arcstats.l2_feeds: 0
> kstat.zfs.misc.arcstats.l2_rw_clash: 0
> kstat.zfs.misc.arcstats.l2_writes_sent: 0
> kstat.zfs.misc.arcstats.l2_writes_done: 0
> kstat.zfs.misc.arcstats.l2_writes_error: 0
> kstat.zfs.misc.arcstats.l2_writes_hdr_miss: 0
> kstat.zfs.misc.arcstats.l2_evict_lock_retry: 0
> kstat.zfs.misc.arcstats.l2_evict_reading: 0
> kstat.zfs.misc.arcstats.l2_free_on_write: 0
> kstat.zfs.misc.arcstats.l2_abort_lowmem: 0
> kstat.zfs.misc.arcstats.l2_cksum_bad: 0
> kstat.zfs.misc.arcstats.l2_io_error: 0
> kstat.zfs.misc.arcstats.l2_size: 0
> kstat.zfs.misc.arcstats.l2_hdr_size: 0
> kstat.zfs.misc.arcstats.memory_throttle_count: 39958287

> kstat.zfs.misc.arcstats.hits: 70211
> kstat.zfs.misc.arcstats.misses: 4902
> kstat.zfs.misc.arcstats.demand_data_hits: 50240
> kstat.zfs.misc.arcstats.demand_data_misses: 2813
> kstat.zfs.misc.arcstats.demand_metadata_hits: 19971
> kstat.zfs.misc.arcstats.demand_metadata_misses: 2089
> kstat.zfs.misc.arcstats.prefetch_data_hits: 0
> kstat.zfs.misc.arcstats.prefetch_data_misses: 0
> kstat.zfs.misc.arcstats.prefetch_metadata_hits: 0
> kstat.zfs.misc.arcstats.prefetch_metadata_misses: 0
> kstat.zfs.misc.arcstats.mru_hits: 28017
> kstat.zfs.misc.arcstats.mru_ghost_hits: 8
> kstat.zfs.misc.arcstats.mfu_hits: 42194
> kstat.zfs.misc.arcstats.mfu_ghost_hits: 0
> kstat.zfs.misc.arcstats.deleted: 195
> kstat.zfs.misc.arcstats.recycle_miss: 0
> kstat.zfs.misc.arcstats.mutex_miss: 0
> kstat.zfs.misc.arcstats.evict_skip: 1571
> kstat.zfs.misc.arcstats.hash_elements: 6036
> kstat.zfs.misc.arcstats.hash_elements_max: 6043
> kstat.zfs.misc.arcstats.hash_collisions: 781
> kstat.zfs.misc.arcstats.hash_chains: 454
> kstat.zfs.misc.arcstats.hash_chain_max: 3
> kstat.zfs.misc.arcstats.p: 283834368
> kstat.zfs.misc.arcstats.c: 427653120
> kstat.zfs.misc.arcstats.c_min: 53456640
> kstat.zfs.misc.arcstats.c_max: 427653120
> kstat.zfs.misc.arcstats.size: 409581888
> kstat.zfs.misc.arcstats.hdr_size: 1261312
> kstat.zfs.misc.arcstats.l2_hits: 0
> kstat.zfs.misc.arcstats.l2_misses: 0
> kstat.zfs.misc.arcstats.l2_feeds: 0
> kstat.zfs.misc.arcstats.l2_rw_clash: 0
> kstat.zfs.misc.arcstats.l2_writes_sent: 0
> kstat.zfs.misc.arcstats.l2_writes_done: 0
> kstat.zfs.misc.arcstats.l2_writes_error: 0
> kstat.zfs.misc.arcstats.l2_writes_hdr_miss: 0
> kstat.zfs.misc.arcstats.l2_evict_lock_retry: 0
> kstat.zfs.misc.arcstats.l2_evict_reading: 0
> kstat.zfs.misc.arcstats.l2_free_on_write: 0
> kstat.zfs.misc.arcstats.l2_abort_lowmem: 0
> kstat.zfs.misc.arcstats.l2_cksum_bad: 0
> kstat.zfs.misc.arcstats.l2_io_error: 0
> kstat.zfs.misc.arcstats.l2_size: 0
> kstat.zfs.misc.arcstats.l2_hdr_size: 0
> kstat.zfs.misc.arcstats.memory_throttle_count: 0


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