[OmniOS-discuss] write amplification zvol

Thu Sep 28 09:48:18 UTC 2017

Thanks for you help Stephan.

i have tried differents LUN with default of 512b and 4096:

LU Name: 600144F04D4F0600000059A588910001
    Operational Status: Online
    Provider Name     : sbd
    Alias             : /dev/zvol/rdsk/filervm2/hdd-110002b
    View Entry Count  : 1
    Data File         : /dev/zvol/rdsk/filervm2/hdd-110002b
    Meta File         : not set
    Size              : 26843545600
    Block Size        : 4096
    Management URL    : not set
    Vendor ID         : SUN
    Product ID        : COMSTAR
    Serial Num        : not set
    Write Protect     : Disabled
    Writeback Cache   : Disabled
    Access State      : Active

Problem is the same.

Cheers,

Anthony

2017-09-28 10:33 GMT+02:00 Stephan Budach <stephan.budach at jvm.de>:

> ----- Ursprüngliche Mail -----
>
> > Von: "anthony omnios" <icoomnios at gmail.com>
> > An: "Richard Elling" <richard.elling at richardelling.com>
> > CC: omnios-discuss at lists.omniti.com
> > Gesendet: Donnerstag, 28. September 2017 09:56:42
> > Betreff: Re: [OmniOS-discuss] write amplification zvol
>
> > 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
> >
>
> How did you setup your LUNs? Especially, what is the block size for those
> LUNs. Could it be, that you went with the default of 512b blocks, where the
> drives do have 4k or even 8k blocks?
>
> Cheers,
> Stephan
>
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