[PVE-User] Proxmox with ceph storage VM performance strangeness

[Rainer Krienke]

hello,

there is no single workload, but a bunch of VMs the do a lot of
different things many of which do not special performance
demands. The VMs that do need speed are NFS Fileservers and SMBservers.

And exactly these servers seem to benefit from the larger block size.
The two I tested mostly on are fileservers.

Aside from  bonnie++ I also tested writing and reading files especially
many small ones. This also works very good and a fact that at the
beginning of my search was not true is now: The proxmox/ceph solution is
faster and in some disciplines much faster than the old xenbased with
ISCSI storage as a backend.

Thanks
Rainer

Am 21.04.20 um 16:01 schrieb Alwin Antreich:
> On Tue, Apr 21, 2020 at 03:34:47PM +0200, Rainer Krienke wrote:
>> Hello,
>>
>> just wanted to thank you for your help and to tell you that I found the
>> culprit that made my read-perfomance look rarther small on a proxmox VM
>> with a LV based on 4 disks (rdbs). The best result using bonnie++ as a
>> test was about 100MBytes/sec on a single VM read performance.
>>
>> I remembered that right after I switched to LVM striping I had tested
>> the default block size LVM would use which was 64K. I found this value
>> rather small and replaces it by 512K, which increased read and write
>> speed.
>>
>> I remenbered this fact and again changed the stripe size to the default
>> RBD object size which is 4MB. Using this value the read performance went
>> up to 400MBytes/sec and if I run two bonnies on two different VMs the
>> total read performance in ceph is about 800MBytes/sec
>> The write performance in this 2VMs test is about 1.2GByte/sec.
> The 4 MB chunk size is good for Ceph. But how is the intended workload
> performing on those VMs?
> 
> --
> Cheers,
> Alwin
> 
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Rainer Krienke, Uni Koblenz, Rechenzentrum, A22, Universitaetsstrasse  1
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