[ClusterLabs] Antw: RES: Performance of a mirrored LV (cLVM) with OCFS: Attempt to monitor it

[Ulrich Windl]

Hi!

Thanks for this info. We actually run the "noop" scheduler for  the SAN
storage (as per menufacturer's recommendation), because on "disk" is actually
spread over up to 40 disks.
Other settings we changes was:
queue/rotational:0
queue/add_random:0
queue/max_sectors_kb:128 (manufacturer's recommendation, before up to 1MB
transfers were seen)
queue/read_ahead_kb:0

And we apply those setting (where available) the the whole stack (disk
devices, multipath device, LV).

Regards,
Ulrich

>>> "Carlos Xavier" <cbastos at connection.com.br> schrieb am 25.05.2016 um 22:25
in
Nachricht <01da01d1b6c3$8f5c3dc0$ae14b940$@com.br>:
> Hi.
> 
> I have been running OCFS2 on clusters for quite long time.
> We started running it over DRBD and now we have it running on a Dell 
> storage.
> Over DRBD it showed a very poor performance, most because the way DRBD 
> works.
> To improve the performance we had to change the I/O Scheduler of the disk to

> "Deadline"
> 
> When we migrate the system to the storage, the issue show up again. 
> Sometimes the system was hanging due to disk access, to solve the issue I 
> changed the I/O Schedule To Deadline and the trouble vanished.
> 
> Regards,
> Carlos.
> 
> 
>> -----Mensagem original-----
>> De: Kristoffer Grönlund [mailto:kgronlund at suse.com]
>> Enviada em: quarta-feira, 25 de maio de 2016 06:55
>> Para: Ulrich Windl; users at clusterlabs.org 
>> Assunto: Re: [ClusterLabs] Performance of a mirrored LV (cLVM) with OCFS: 
> Attempt to monitor it
>> 
>> Ulrich Windl <Ulrich.Windl at rz.uni-regensburg.de> writes:
>> 
>> > cLVM has never made a good impression regarding performance, so I wonder
if 
> there's anything we
>> could do to improve the4 performance. I suspect that one VM paging heavily

> on OCFS2 kills the
>> performance of the whole cluster (that hosts Xen PV guests only). Anyone 
> with deeper insights?
>> 
>> My understanding is that this is a problem inherent in the design of CLVM 
> and there is work ongoing to
>> mitigate this by handling clustering in md instead. See this LWN article
for 
> more details:
>> 
>> http://lwn.net/Articles/674085/ 
>> 
>> Cheers,
>> Kristoffer
>> 
>> --
>> // Kristoffer Grönlund
>> // kgronlund at suse.com 
>> 
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