KVM disk io caching for LVM over iSCSI (cache=writethrough!)

[adis]

Just a quick remark for LVM over iSCSI setup, as suggested by wiki article:

http://pve.proxmox.com/wiki/Storage_Model#LVM_Groups_with_Network_Backing


The problem is that Proxmox creates virtual disks with cache=none, but iSCSI works much better with cache=writethrough
This can easily be checked by running bonnie+ or similar concurrent disk benchmark.

With cache=none CPU load on both, hypervisor and guest, is very high. Performance is reasonable.
WIth cache=writethrough, CPU load is pretty high (but within expectations, and much lower compared to cache=none), and performace is excellent.

 

[macday]

What about this cache-setting on drbd ?