[OmniOS-discuss] write amplification zvol
anthony omnios
icoomnios at gmail.com
Thu Sep 28 07:56:42 UTC 2017
Thanks Richard for your help.
My problem is that i have a network ISCSI traffic of 2 MB/s, each 5 seconds
i need to write on disks 10 MB of network traffic but on pool filervm2 I am
writing much more that, approximatively 60 MB each 5 seconds. Each ssd of
filervm2 is writting 15 MB every 5 second. When i check with smartmootools
every ssd is writing approximatively 250 GB of data each day.
How can i reduce amont of data writting on each ssd ? i have try to reduce
block size of zvol but it change nothing.
Anthony
2017-09-28 1:29 GMT+02:00 Richard Elling <richard.elling at richardelling.com>:
> Comment below...
>
> > On Sep 27, 2017, at 12:57 AM, anthony omnios <icoomnios at gmail.com>
> wrote:
> >
> > Hi,
> >
> > i have a problem, i used many ISCSI zvol (for each vm), network traffic
> is 2MB/s between kvm host and filer but i write on disks many more than
> that. I used a pool with separated mirror zil (intel s3710) and 8 ssd
> samsung 850 evo 1To
> >
> > zpool status
> > pool: filervm2
> > state: ONLINE
> > scan: resilvered 406G in 0h22m with 0 errors on Wed Sep 20 15:45:48
> 2017
> > config:
> >
> > NAME STATE READ WRITE CKSUM
> > filervm2 ONLINE 0 0 0
> > mirror-0 ONLINE 0 0 0
> > c7t5002538D41657AAFd0 ONLINE 0 0 0
> > c7t5002538D41F85C0Dd0 ONLINE 0 0 0
> > mirror-2 ONLINE 0 0 0
> > c7t5002538D41CC7105d0 ONLINE 0 0 0
> > c7t5002538D41CC7127d0 ONLINE 0 0 0
> > mirror-3 ONLINE 0 0 0
> > c7t5002538D41CD7F7Ed0 ONLINE 0 0 0
> > c7t5002538D41CD83FDd0 ONLINE 0 0 0
> > mirror-4 ONLINE 0 0 0
> > c7t5002538D41CD7F7Ad0 ONLINE 0 0 0
> > c7t5002538D41CD7F7Dd0 ONLINE 0 0 0
> > logs
> > mirror-1 ONLINE 0 0 0
> > c4t2d0 ONLINE 0 0 0
> > c4t4d0 ONLINE 0 0 0
> >
> > i used correct ashift of 13 for samsung 850 evo
> > zdb|grep ashift :
> >
> > ashift: 13
> > ashift: 13
> > ashift: 13
> > ashift: 13
> > ashift: 13
> >
> > But i write a lot on ssd every 5 seconds (many more than the network
> traffic of 2 MB/s)
> >
> > iostat -xn -d 1 :
> >
> > r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
> > 11.0 3067.5 288.3 153457.4 6.8 0.5 2.2 0.2 5 14 filervm2
>
> filervm2 is seeing 3067 writes per second. This is the interface to the
> upper layers.
> These writes are small.
>
> > 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 rpool
> > 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c4t0d0
> > 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c4t1d0
> > 0.0 552.6 0.0 17284.0 0.0 0.1 0.0 0.2 0 8 c4t2d0
> > 0.0 552.6 0.0 17284.0 0.0 0.1 0.0 0.2 0 8 c4t4d0
>
> The log devices are seeing 552 writes per second and since sync=standard
> that
> means that the upper layers are requesting syncs.
>
> > 1.0 233.3 48.1 10051.6 0.0 0.0 0.0 0.1 0 3
> c7t5002538D41657AAFd0
> > 5.0 250.3 144.2 13207.3 0.0 0.0 0.0 0.1 0 3
> c7t5002538D41CC7127d0
> > 2.0 254.3 24.0 13207.3 0.0 0.0 0.0 0.1 0 4
> c7t5002538D41CC7105d0
> > 3.0 235.3 72.1 10051.6 0.0 0.0 0.0 0.1 0 3
> c7t5002538D41F85C0Dd0
> > 0.0 228.3 0.0 16178.7 0.0 0.0 0.0 0.2 0 4
> c7t5002538D41CD83FDd0
> > 0.0 225.3 0.0 16210.7 0.0 0.0 0.0 0.2 0 4
> c7t5002538D41CD7F7Ed0
> > 0.0 282.3 0.0 19991.1 0.0 0.0 0.0 0.2 0 5
> c7t5002538D41CD7F7Dd0
> > 0.0 280.3 0.0 19871.0 0.0 0.0 0.0 0.2 0 5
> c7t5002538D41CD7F7Ad0
>
> The pool disks see 1989 writes per second total or 994 writes per second
> logically.
>
> It seems to me that reducing 3067 requested writes to 994 logical writes
> is the opposite
> of amplification. What do you expect?
> -- richard
>
> >
> > I used zvol of 64k, i try with 8k and problem is the same.
> >
> > zfs get all filervm2/hdd-110022a :
> >
> > NAME PROPERTY VALUE SOURCE
> > filervm2/hdd-110022a type volume -
> > filervm2/hdd-110022a creation Tue May 16 10:24 2017 -
> > filervm2/hdd-110022a used 5.26G -
> > filervm2/hdd-110022a available 2.90T -
> > filervm2/hdd-110022a referenced 5.24G -
> > filervm2/hdd-110022a compressratio 3.99x -
> > filervm2/hdd-110022a reservation none
> default
> > filervm2/hdd-110022a volsize 25G local
> > filervm2/hdd-110022a volblocksize 64K -
> > filervm2/hdd-110022a checksum on
> default
> > filervm2/hdd-110022a compression lz4 local
> > filervm2/hdd-110022a readonly off
> default
> > filervm2/hdd-110022a copies 1
> default
> > filervm2/hdd-110022a refreservation none
> default
> > filervm2/hdd-110022a primarycache all
> default
> > filervm2/hdd-110022a secondarycache all
> default
> > filervm2/hdd-110022a usedbysnapshots 15.4M -
> > filervm2/hdd-110022a usedbydataset 5.24G -
> > filervm2/hdd-110022a usedbychildren 0 -
> > filervm2/hdd-110022a usedbyrefreservation 0 -
> > filervm2/hdd-110022a logbias latency
> default
> > filervm2/hdd-110022a dedup off
> default
> > filervm2/hdd-110022a mlslabel none
> default
> > filervm2/hdd-110022a sync standard local
> > filervm2/hdd-110022a refcompressratio 3.99x -
> > filervm2/hdd-110022a written 216K -
> > filervm2/hdd-110022a logicalused 20.9G -
> > filervm2/hdd-110022a logicalreferenced 20.9G -
> > filervm2/hdd-110022a snapshot_limit none
> default
> > filervm2/hdd-110022a snapshot_count none
> default
> > filervm2/hdd-110022a redundant_metadata all
> default
> >
> > Sorry for my bad english.
> >
> > What can be the problem ? thanks
> >
> > Best regards,
> >
> > Anthony
> >
> >
> > _______________________________________________
> > OmniOS-discuss mailing list
> > OmniOS-discuss at lists.omniti.com
> > http://lists.omniti.com/mailman/listinfo/omnios-discuss
>
>
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