[PVE-User] Proxmox + ZFS: Performance issues

[Ralf]

Hi,

I think my SATA cables should be fine, as dumping from the raw block
device yields to 100MiB/s. I even tried offlining one disk and then
checked performance: Still bad.

But I don't get the point. If SATA cables were broken, how can I get
good performance on raw block devices? Nevertheless, I have no clue
what's going on, so i'll give it a try.

  Ralf

On 04/24/2016 06:57 PM, Adam Thompson wrote:
> Perhaps irrelevant,  but a colleague of mine recently solved a puzzling performance issue merely by replacing the existing SATA cables with new, properly-rated cables.
> Turns out, much like USB v1 vs USB v2, there's next to nothing distinguishing SATA I cables vs SATA II cables vs SATA III cables, except for unusually poor performance when used at too high a speed.
> Only the magnitude of your performance drop suggests this; also the fact that you get good raw read performance, which mirrors the symptoms in the SATA cable case precisely.
> -Adam
>
> On April 24, 2016 11:49:38 AM CDT, Robert Fantini <robertfantini at gmail.com> wrote:
>> if those are not ssd drives, then  adding a zil drive will most likely
>> help.
>>
>> On Sat, Apr 23, 2016 at 2:15 PM, Ralf <ralf+pve at ramses-pyramidenbau.de>
>> wrote:
>>
>>> 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
>>> _______________________________________________
>>> pve-user mailing list
>>> pve-user at pve.proxmox.com
>>> http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user
>>>
>> _______________________________________________
>> pve-user mailing list
>> pve-user at pve.proxmox.com
>> http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-user