suddenly slow writes on XFS Filesystem

[Stefan Priebe]

Hi,

since a few days i've experienced a really slow fs on one of our backup 
systems.

I'm not sure whether this is XFS related or related to the Controller / 
Disks.

It is a raid 10 of 20 SATA Disks and i can only write to them with about 
700kb/s while doing random i/o. I tried vanilla Kernel 3.0.30 and 3.3.4 
- no difference. Writing to another partition on another xfs array works 
fine.

Details:
#~ df -h
/dev/sdb1             4,6T  4,4T  207G  96% /mnt

#~ df -i
/dev/sdb1            4875737052 4659318044 216419008  96% /mnt

#~ xfs_db -c frag -r /dev/sdb1
actual 83160469, ideal 82145389, fragmentation factor 1,22%

#~ xfs_info /dev/sdb1
meta-data=/dev/sdb1              isize=256    agcount=5, 
agsize=268435392 blks
          =                       sectsz=512   attr=2
data     =                       bsize=4096   blocks=1218967031, imaxpct=5
          =                       sunit=64     swidth=1280 blks
naming   =version 2              bsize=4096   ascii-ci=0
log      =internal               bsize=4096   blocks=32768, version=2
          =                       sectsz=512   sunit=64 blks, lazy-count=0
realtime =none                   extsz=4096   blocks=0, rtextents=0

#~ cat /proc/mounts
/dev/sdb1 /mnt xfs 
rw,noatime,nodiratime,attr2,nobarrier,logbufs=8,logbsize=256k,sunit=512,swidth=10240,prjquota 
0 0

Any ideas?

Stefan