[Linux-cluster] GFS2 poor performance

[Fabiano F. Vitale]

 Setting demote_secs to 30 and glock_purge to 70 in a gfs filesystem 
increased frightfully performance of commands like ls, df, in a directory 
that has many files.
But the gfs2 filesystem doesn't have the attribute glock_purge to tune.
Exists any attribute  in gfs2 in place of glock_purge which exists only in 
gfs1

thanks

Fabiano


----- Original Message ----- 
From: "Jeff Sturm" <jeff.sturm at eprize.com>
To: "linux clustering" <linux-cluster at redhat.com>
Sent: Thursday, November 06, 2008 5:53 PM
Subject: RE: [Linux-cluster] GFS2 poor performance


>I looked over the summit document you referenced below.  The value of 
>demote_secs mentioned is an example setting, and unfortunately no 
>recommendations or rationale accompany this.
>
> For some access patterns you can get better performance by actually 
> increasing demote_secs.  For example, we have a node that we routinely 
> rsync a file tree onto using a GFS partition.  Increasing demote_secs from 
> 300 to 86400 reduced the average rsync time by a factor of about 4.  The 
> reason is that this node has little lock contention and needs to lock each 
> file every time we start an rsync process.  With demote_secs=300, it was 
> doing much more work to reacquire locks on each run.  Whereas 
> demote_secs=86400 allowed the locks to persist up to a day, since the 
> overall number of files in our application is bounded such that they will 
> fit in buffer cache, together with locks.
>
> At another extreme, we have an application that creates a lot of files but 
> seldom opens them on the same node.  In this case there is no value in 
> holding onto the locks, so we set demote_secs to a small value and 
> glock_purge as high as 70 to ensure locks are quickly released in memory.
>
> The best advice I can give in general is to experiment with different 
> settings for demote_secs and glock_purge while watching the output of 
> "gfs_tool counters" to see how they behave.
>
> Jeff
>
> -----Original Message-----
> From: linux-cluster-bounces at redhat.com 
> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Fabiano F. Vitale
> Sent: Tuesday, November 04, 2008 3:19 PM
> To: linux clustering
> Subject: Re: [Linux-cluster] GFS2 poor performance
>
> Hi,
>
> for cluster purpose the two nodes are linked by a  patch cord cat6 and the 
> lan interfaces are gigabit.
>
> All nodes have a Fibre Channel Emulex Corporation Zephyr-X LightPulse and 
> the Storage is a HP EVA8100
>
> I read the document
> http://www.redhat.com/promo/summit/2008/downloads/pdf/Thursday/Summit08presentation_GFSBestPractices_Final.pdf
> which show some parameters to tune and one of  them is  demote_secs, to 
> adjust to 100sec
>
> thanks
>
>> What sort of network and storage device are you using?
>>
>> Also, why set demote_secs so low?
>>
>> -----Original Message-----
>> From: linux-cluster-bounces at redhat.com
>> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of ffv at tjpr.jus.br
>> Sent: Tuesday, November 04, 2008 2:13 PM
>> To: linux-cluster at redhat.com
>> Subject: [Linux-cluster] GFS2 poor performance
>>
>> Hi all,
>>
>> I´m getting a very poor performance using GFS2.
>> I have two qmail (mail) servers and one gfs2 filesystem shared by them.
>> In this case, each directory in GFS2 filesystem may have upon to 10000
>> files (mails)
>>
>> The problem is in performance of some operations like ls, du, rm, etc
>> for example,
>>
>> # time du -sh /dados/teste
>> 40M     /dados/teste
>>
>> real    7m14.919s
>> user    0m0.008s
>> sys     0m0.129s
>>
>> this is unacceptable
>>
>> Some attributes i already set using gfs2_tool:
>>
>> gfs2_tool settune /dados demote_secs 100 gfs2_tool setflag jdata
>> /dados gfs2_tool setflag sync /dados gfs2_tool setflag directio /dados
>>
>> but the performance is still very bad
>>
>>
>> Anybody know how to tune the filesystem for a acceptable performance
>> working with directory with 10000 files?
>> thanks for any help
>>
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