[PVE-User] Proxmox + ZFS: Performance issues

Yannis Milios yannis.milios at gmail.com
Tue Apr 26 00:30:21 CEST 2016

Hi Ralf,

Are both hard drives exactly the same model?

I've noticed that your drive uses 512byte sector size (instead of 4K 
sector size which is the current trend).

In that case, is your pool properly aligned to ashift=9 ?

More info here: 



On 04/25/2016 09:38 PM, Ralf wrote:
> On 04/25/2016 10:14 PM, Lindsay Mathieson wrote:
>> On 25/04/2016 11:43 PM, Ralf wrote:
>>> some more random analysis:
>>> I used atop to debug the problem.
>>> Turned out, that disks are 100% busy and the average io time is beyond
>>> all hope. ZFS seems to read/write/arrange things in a random and not in
>>> a sequential way.
>> What does "iotop -P --only" show?
> That dd is using 100% of io. Ram usage is 5/10 GiB at the moment, so
> more than enough free ram.
>> I suspect lack of ram is your problem.
> Why do I need so much RAM for mirror raid? All ram-intensive features
> are turned off.
>    Ralf
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