[sheepdog-users] Object Cache Question

[Bastian Scholz]

Hi List,

I try around with object cache of sheepdog in my
Testcluster (3 nodes, copies=3).

For this, I start an additional gateway sheep
process on one node (separated disk for cache but
same type as the obj disks). But when enabling
Object Cache, the rw performance of random 4k
rw drops to 1/10th of the speed without OC enabled.

# sheep --version
Sheepdog daemon version 0.7.7

# qemu --version
QEMU emulator version 1.1.2 (Debian 1.1.2+dfsg-6a)

# virsh --version
0.9.12.3

qemu cache setting is none (managed by libvirt), but
it didnt make any noticeable difference when set to
writeback or writethrough...

# sheep /mnt/soeren/3/ -g -p 7003
# fio guest results
read : io=11612KB, bw=594415 B/s, iops=145 , runt= 20004msec
write: io=11804KB, bw=604243 B/s, iops=147 , runt= 20004msec

# sheep /mnt/soeren/3/ -g -p 7003 -w size=10G
# fio guest results
read : io=1172.0KB, bw=59934 B/s, iops=14 , runt= 20024msec
write: io=1256.0KB, bw=64230 B/s, iops=15 , runt= 20024msec

For comparison the fio results of the sheep
cache directory.

read : io=10576KB, bw=541355 B/s, iops=132 , runt= 20005msec
write: io=10712KB, bw=548317 B/s, iops=133 , runt= 20005msec

Any Ideas whats wrong? Maybe some Problems with
the old QEMU Version?

Cheers
Bastian