[PVE-User] Proxmox + ZFS: Performance issues

[Ralf]

Hi,

I encounter very bad read/write performance on my mirror-zfs, even on
hypervisor-side.

After shutting down all VMs, reading and writing from raw ZFS block
devices VMs runs at maximum 5MiB/s (tested with dd
if=/dev/rpool/VM/disk-100 of=/dev/null) while reading from the
underlying raw-disk (/dev/sda) has good performance (~100MiB/s). Of
course, performance inside VMs is even worse. Any ideas?

This is my setup:
Proxmox / 4.1-30/9e199213 / Linux 4.4.6-1-pve / ZFS mirror, two disks

ZFS setup:

$ dmesg | grep ZFS  
[    2.882118] ZFS: Loaded module v0.6.5.6-1, ZFS pool version 5000, ZFS
filesystem version 5

$ zpool status
        [snip]
        NAME        STATE     READ WRITE CKSUM
        rpool       ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            sdb2    ONLINE       0     0     0
            sda2    ONLINE       0     0     0

ZFS module parameters:
$ cat /etc/modprobe/zfs.conf
options zfs zfs_arc_max=3221225472

Partition alignement:
$ parted /dev/sda
(parted) align-check o 2                                                 
2 aligned

Dedup: off
Checksumming: on
Compression: off

Anything helps!

Cheers
  Ralf