[Ocfs2-users] ocfs2 hangs during webserver usage

[Luis Freitas]

David,

  You probably could get away with writing the log files to OCFS2, but in different files.

   The access_log gets a small write on each access, and writes will be serialized, since no two processes can write to it at the same time.

   So it should be related more to the size of the disk queues and the speed of the interconnect than to the speed of the SAN itself. If you keep writing to the same file from different nodes, OCFS2 will need to keep flushing pages and bouncing write locks from one node to another on each page hit. This is very nonscalable, as you got a single serialized write on each page access.

   The extent size would play a role on this also, as Sunil pointed. You could check if the extent size is different on your test environment. The mkfs tool might have defaulted a larger extent size if the total size of the filesystem is larger. (Sunil, correct me on this if I am wrong).

Regards,
Luis
   

--- On Tue, 1/27/09, jmoseley at corp.xanadoo.com <jmoseley at corp.xanadoo.com> wrote:
From: jmoseley at corp.xanadoo.com <jmoseley at corp.xanadoo.com>
Subject: Re: [Ocfs2-users] ocfs2 hangs during webserver usage
To: "David Johle" <djohle at industrialinfo.com>
Cc: lfreitas34 at yahoo.com, ocfs2-users at oss.oracle.com, ocfs2-users-bounces at oss.oracle.com
Date: Tuesday, January 27, 2009, 10:32 PM

As others have indicated, I don't think that's going to work very well.
You've got two different nodes trying to write to the same file constantly.
I would keep each server's log on a locally mounted file system, or simply
keep the logs on the OCFS2 filesystem, but have each node write to
different log files.

Yeah, that makes parsing access_logs slightly more of a problem for
producing hit reports, etc, but I think you'll notice performance improve.


James Moseley




                                                                           
             David Johle                                                   
             <djohle at industria                                             
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                                                                   Subject 
                                       Re: [Ocfs2-users] ocfs2 hangs       
             01/27/2009 04:38          during webserver usage              
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Yes, that is the case, multiple nodes with the same log file open &
being written to at once.

Worked well during all my testing environment stress tests, and even
worked great in production for over a month.



At 02:56 PM 1/27/2009, Luis Freitas wrote:
>David,
>
>     You said you were keeping the apache log files on OCFS2.
>
>      Are you using the same log file (access_log and error_log) for
> all the nodes? That is a single access_log that is writen by both
> nodes simultaneosly?
>
>Regards,
>Luis


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