[linux-lvm] huge performance problems 25kb/s write speed

[Cristian Livadaru]

I have since yesterday huge performance problems on my LVM!
I have 2x 300GB as 1 unstriped LVM.

dd if=/dev/zero of=dd.txt count=500
500+0 records in
500+0 records out
256000 bytes transferred in 9.999764 seconds (25601 bytes/sec)

dd if=/dev/zero of=dd.txt count=500 bs=4096
500+0 records in
500+0 records out
2048000 bytes transferred in 10.020213 seconds (204387 bytes/sec)

After a reboot it worked normal again for a while, now I have the  
same problem again.

esplendidos:~# pvs
   PV         VG      Fmt  Attr PSize   PFree
   /dev/hde1  sharevg lvm2 a-   279.45G      0
   /dev/hdg1  sharevg lvm2 a-   279.45G   4.00M

esplendidos:~# lvs
   LV         VG      Attr   LSize   Origin Snap%  Move Copy%
   sharelv    sharevg -wi-ao 558.90G

esplendidos:~# vgs
   VG      #PV #LV #SN Attr  VSize   VFree
   sharevg   2   1   0 wz--n 558.91G   4.00M


   --- Volume group ---
   VG Name               sharevg
   System ID
   Format                lvm2
   Metadata Areas        2
   Metadata Sequence No  2
   VG Access             read/write
   VG Status             resizable
   MAX LV                0
   Cur LV                1
   Open LV               1
   Max PV                0
   Cur PV                2
   Act PV                2
   VG Size               558.91 GB
   PE Size               4.00 MB
   Total PE              143080
   Alloc PE / Size       143079 / 558.90 GB
   Free  PE / Size       1 / 4.00 MB
   VG UUID               LaGWNF-9Ace-li4f-h8z2-SJYk-YeyB-joXznp


   --- Logical volume ---
   LV Name                /dev/sharevg/sharelv
   VG Name                sharevg
   LV UUID                zCe6sI-pglI-7yh1-EnL4-gsKo-FOEb-POyVoL
   LV Write Access        read/write
   LV Status              available
   # open                 1
   LV Size                558.90 GB
   Current LE             143079
   Segments               2
   Allocation             inherit
   Read ahead sectors     0
   Block device           253:8

   --- Physical volume ---
   PV Name               /dev/hde1
   VG Name               sharevg
   PV Size               279.45 GB / not usable 0
   Allocatable           yes (but full)
   PE Size (KByte)       4096
   Total PE              71540
   Free PE               0
   Allocated PE          71540
   PV UUID               g3jfAR-Z2Ka-SCgr-08QB-8WBn-5g4h-jXLrn1

   --- Physical volume ---
   PV Name               /dev/hdg1
   VG Name               sharevg
   PV Size               279.45 GB / not usable 0
   Allocatable           yes
   PE Size (KByte)       4096
   Total PE              71540
   Free PE               1
   Allocated PE          71539
   PV UUID               kYQB4j-fYV9-3NUa-g0Sg-H4Bk-Kx5F-wRO9G1


hdparm -tT /dev/hde

/dev/hde:
Timing cached reads:   952 MB in  2.00 seconds = 476.00 MB/sec
Timing buffered disk reads:  130 MB in  3.00 seconds =  43.33 MB/sec
esplendidos:/shared# hdparm -tT /dev/hdg

/dev/hdg:
Timing cached reads:   960 MB in  2.00 seconds = 480.00 MB/sec
Timing buffered disk reads:  154 MB in  3.01 seconds =  51.16 MB/sec


I don't have any errors in logfiles ( syslog/messages/lvm2.log )
Any hints what else I can check or do to improve performance? I mean  
25kb/s on a local HD is more then just slow!
Please please help.


--
Cristian Livadaru
http://livadaru.net