[OmniOS-discuss] write amplification zvol
anthony omnios
icoomnios at gmail.com
Wed Sep 27 07:57:28 UTC 2017
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
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
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
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
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