Hello,
I've migrated my system to btrfs (raid1) a few months ago. Since then
the performance has been pretty bad, but recently it's gotten
unbearable: a simple sync called while the system is idle can take 20 up
to 60 seconds. Creating or deleting files often has several seconds
latency, too.
One curious - but maybe unrelated - observation is that even though I'm
using a raid1 btrfs setup, the hdds are often being written to
sequentially. One hard-drive sees some write activity and after it
subsides, the other drive sees some activity. (See attached
sequential-writes.txt.)
- 64bit gentoo with vanilla 2.6.39 kernel
- lzo compression enabled
- 2x WD1000FYPS (1TB WD hdds)
- Athlon x2 2.2GHz with 8GB RAM
- space_cache was enabled, but it seemed to make the problem worse.
It's no longer in the mount options.
Any help is appreciated. Thanks,
Henning
server ~ # sync; time sync
real 0m28.869s
user 0m0.000s
sys 0m5.750s
server ~ # uname -a
Linux server 2.6.39 #3 SMP Sat May 28 17:25:31 CEST 2011 x86_64 AMD
Athlon(tm) 64 X2 Dual Core Processor 4200+ AuthenticAMD GNU/Linux
server ~ # mount | grep btrfs
/dev/sdb2 on / type btrfs (rw,noatime,compress=lzo,noacl)
/dev/sda2 on /mnt/pool type btrfs (rw,noatime,subvolid=0,compress=lzo)
/dev/sda2 on /usr/portage type btrfs
(rw,noatime,subvol=newportage,compress=lzo)
/dev/sda2 on /home type btrfs (rw,noatime,subvol=home,compress=lzo)
/dev/sda2 on /home/mythtv type btrfs
(rw,noatime,subvol=mythtv,compress=lzo)
server ~ # btrfs fi show
Label: none uuid: 7676eb78-e411-4505-ac51-ccd12aa5a6b6
Total devices 2 FS bytes used 281.58GB
devid 1 size 931.28GB used 898.26GB path /dev/sda2
devid 3 size 931.27GB used 898.26GB path /dev/sdb2
Btrfs v0.19-35-g1b444cd-dirty
server ~ # btrfs fi df /
Data, RAID1: total=875.00GB, used=279.30GB
System, RAID1: total=8.00MB, used=140.00KB
System: total=4.00MB, used=0.00
Metadata, RAID1: total=23.25GB, used=2.28GB
bonnie++
Version 1.96 ------Sequential Output------ --Sequential Input-
--Random-
Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP
/sec %CP
server 16G 147 90 76321 18 31787 16 1370 71 64812 14
27.0 66
Latency 66485us 7581ms 4455ms 25011us 695ms
959ms
Version 1.96 ------Sequential Create------ --------Random
Create--------
server -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
/sec %CP
16 238 51 +++++ +++ 219 51 284 52 +++++ +++
390 57
Latency 1914ms 524us 3461ms 1141ms 39us
1308ms
1.96,1.96,server,1,1308618030,16G,,147,90,76321,18,31787,16,1370,71,64812,14,27.0,66,16,,,,,238,51,+++++,+++,219,51,284,52,+++++,+++,390,57,66485us,7581ms,4455ms,25011us,695ms,959ms,1914ms,524us,3461ms,1141ms,39us,1308ms
server ~ # iostat -m 5
avg-cpu: %user %nice %system %iowait %steal %idle
3.00 0.00 45.20 5.20 0.00 46.60
Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
sda 0.00 0.00 0.00 0 0
sdb 15.20 0.06 0.00 0 0
md0 0.00 0.00 0.00 0 0
avg-cpu: %user %nice %system %iowait %steal %idle
4.30 0.00 37.46 42.36 0.00 15.88
Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
sda 45.00 0.00 0.38 0 1
sdb 467.60 0.02 2.06 0 10
md0 0.00 0.00 0.00 0 0
avg-cpu: %user %nice %system %iowait %steal %idle
4.31 0.00 19.34 58.82 0.00 17.54
Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
sda 8.80 0.00 0.04 0 0
sdb 649.80 0.02 2.67 0 13
md0 0.00 0.00 0.00 0 0
avg-cpu: %user %nice %system %iowait %steal %idle
3.20 0.00 63.24 31.97 0.00 1.60
Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
sda 585.80 0.00 2.36 0 11
sdb 20.80 0.08 0.16 0 0
md0 0.00 0.00 0.00 0 0
avg-cpu: %user %nice %system %iowait %steal %idle
3.30 0.00 42.60 39.30 0.00 14.80
Device: tps MB_read/s MB_wrtn/s MB_read MB_wrtn
sda 514.20 0.00 2.29 0 11
sdb 59.20 0.10 0.17 0 0
md0 0.00 0.00 0.00 0 0
