[gpfsug-discuss] LROC

[Sven Oehme]

StatCache is not useful on Linux, that hasn't changed if you don't use LROC
on the same node. LROC uses the compact object (StatCache) to store its
pointer to the full file Object which is stored on the LROC device. so on a
call for attributes that are not in the StatCache the object gets recalled
from LROC and converted back into a full File Object, which is why you
still need to have a reasonable maxFiles setting even you use LROC as you
otherwise constantly move file infos in and out of LROC and put the device
under heavy load.

sven



On Wed, Dec 21, 2016 at 12:29 PM Peter Childs <p.childs at qmul.ac.uk> wrote:

> My understanding was the maxStatCache was only used on AIX and should be
> set low on Linux, as raising it did't help and wasted resources. Are we
> saying that LROC now uses it and setting it low if you raise
> maxFilesToCache under linux is no longer the advice.
>
>
> Peter Childs
>
>
> ________________________________________
> From: gpfsug-discuss-bounces at spectrumscale.org <
> gpfsug-discuss-bounces at spectrumscale.org> on behalf of Sven Oehme <
> oehmes at gmail.com>
> Sent: Wednesday, December 21, 2016 9:23:16 AM
> To: gpfsug main discussion list
> Subject: Re: [gpfsug-discuss] LROC
>
> Lroc only needs a StatCache object as it 'compacts' a full open File
> object (maxFilesToCache) to a StatCache Object when it moves the content to
> the LROC device.
> therefore the only thing you really need to increase is maxStatCache on
> the LROC node, but you still need maxFiles Objects, so leave that untouched
> and just increas maxStat
>
> Olaf's comment is important you need to make sure your manager nodes have
> enough memory to hold tokens for all the objects you want to cache, but if
> the memory is there and you have enough its well worth spend a lot of
> memory on it and bump maxStatCache to a high number. i have tested
> maxStatCache up to 16 million at some point per node, but if nodes with
> this large amount of inodes crash or you try to shut them down you have
> some delays , therefore i suggest you stay within a 1 or 2  million per
> node and see how well it does and also if you get a significant gain.
> i did help Bob to setup some monitoring for it so he can actually get
> comparable stats, i suggest you setup Zimon and enable the Lroc sensors to
> have real stats too , so you can see what benefits you get.
>
> Sven
>
> On Tue, Dec 20, 2016 at 8:13 PM Matt Weil <mweil at wustl.edu<mailto:
> mweil at wustl.edu>> wrote:
>
> as many as possible and both
>
> have maxFilesToCache 128000
>
> and maxStatCache 40000
>
> do these effect what sits on the LROC as well?  Are those to small?
> 1million seemed excessive.
>
> On 12/20/16 11:03 AM, Sven Oehme wrote:
> how much files do you want to cache ?
> and do you only want to cache metadata or also data associated to the
> files ?
>
> sven
>
>
>
> On Tue, Dec 20, 2016 at 5:35 PM Matt Weil <mweil at wustl.edu<mailto:
> mweil at wustl.edu>> wrote:
>
> https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/General%20Parallel%20File%20System%20(GPFS)/page/Flash%20Storage
> <
> https://www.ibm.com/developerworks/community/wikis/home?lang=en#%21/wiki/General%20Parallel%20File%20System%20%28GPFS%29/page/Flash%20Storage
> >
>
> Hello all,
>
> Are there any tuning recommendations to get these to cache more metadata?
>
> Thanks
>
> Matt
>
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