[PVE-User] Bad IO Performance in "old" Debian Linux VMs

[Ml Ml]

Hello List,

i am running Proxmox version 4.4 on a 3 Node Full-Meshed Cluster with Ceph.

Everythink works greate, except of the IO Performance on VMs which are Debian 5.
In this Debian 5 VM i run a 2.6.32-bpo.5-amd64 Kernel with virtio and
default cache

I only get about a write speed of about 35MB/sec.

With Debian 8 and 3.16.0-4-amd64 Kernel i get about 130MB/sec (which
is the physical limit).
(also using virtio - default cache)

Is this performance drop with that older Kernel/Dist normal?

If i have a look at dstat whilest doing my IO Test (on Debian 8 and
Kernel 3.12)  i can see much more performance going on the network
interfaces and disk.

Therefore a hardware bottle neck can not be the reason for the bad
performance on Debian 5 and Kernel 2.6.32.

Any ideas (other than Updating from Debian5 to Debian8)?

Thanks,
Mario