[sheepdog-users] object cache questions

Maxim Terletskiy terletskiy at emu.ru
Sat Feb 1 21:09:29 CET 2014

Hi everybody!

First of all I'd like to share my experience in object cache usage. 
Noticed that with object cache on ext4 volume mounted with 
"noatime,nodiratime,user_xattr" mount options my VMs dying in short time 
after start(qemu processes crashing with segfaults). I spent some days 
reading wiki, searching net and rebuilding qemu in attempts to 
understand the reason before found that "nodiratime" is root of the 
evil. Now using ext4 with "noatime,user_xattr" and looks like everything 
is ok. Hope this information would be usefull for somebody.

Now I'm curious about object cache failover. What happen if volume with 
cache will fail? Will sheep and VMs live or will they die?

If they will live is there any way to replace failed volume without 
restarting sheep process (I found that with restart of sheep process VMs 
connected to it dying) or migrating VMs to other host?

Is there any difference in behavior in this cases between 0.7.6 and 0.8.0?

P.S.: Using sheep version 0.7.6 and qemu 1.6.x.

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