[sheepdog-users] object cache and swap

Максим Терлецкий terleckiy at emu.ru
Sun Apr 27 00:21:07 CEST 2014


I'm running VM with 200Gb data on disk at VM node with 110Gb object
cache volume. Tried to run fsck in VM. After writing about 80Gb data to
object cache VM node started to swapping. VM disk performance became
terrible. After some more time I see that object cache is almost 100%
used, swap is 100% used, all free RAM(30Gb from 32Gb physically
available) in top is "cached". Is it normal? How can I prevent VM host
from swapping? I thought about disabling swap at all, but afraid that
node can crash.

My setup is sheep 0.8.0-f06a150, CentOS 6.5 x86_64, qemu 1.7.0, VM disk
cache type is writeback.

sheep options(from ps ax output):
sheep -g -c
-y -w dir=/mnt/sheep_objcache size=110G directio

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