[Ocfs2-users] Slow on open()

[Somsak Sriprayoonsakul]

For our case log file shouldn't be the problem since it's store locally. But
fragmentation might be the cause. We serve a lot of small files (mostly html
and jpg) out of OCFS2. And the file come in and go out very frequently, old
topic will be paged out to archive directory out of OCFS2, while new topic
are created on OCFS2. Thanks for pointing the bug report then.

Right now we are using 4 slots and planning to serving about 4 in near
future. I think we shouldn't decrease the number of slot right now.

Are there any other statistics that we should observe for?

2010/1/28 Brad Plant <bplant at iinet.net.au>

> Hi Somsak,
>
> I observed high loads and apache slowness when there was insufficient
> contiguous free space due to fragmentation. I believe it was because apache
> couldn't write it's log files efficiently. We had 2 apache nodes and I found
> that stopping apache on the problem node resolved the problem until I
> deleted lots of unused files.
>
> My symptoms don't seem to suggest a slow open() syscall like your strace
> results are showing, but I certainly got the high load and poor apache
> performance. It might be worth checking out anyway. There is a bug report
> and we're just waiting for the patch to get reviewed and made publicly
> available.
>
> http://oss.oracle.com/bugzilla/show_bug.cgi?id=1189
>
> Cheers,
>
> Brad
>
>
>
> On Tue, 19 Jan 2010 16:12:07 +0700
> Somsak Sriprayoonsakul <somsaks at gmail.com> wrote:
>
> > Hello,
> >
> > We are using OCFS2 version 1.4.3 on CentOS5, x86_64 with 8GB memory. The
> > underlying storage is HP 2312fc smart array equipped with 12 SAS 15K rpm,
> > configured as RAID10 using 10 HDDs + 2 spares. The array has about 4GB
> > cache. Communication is 4Gbps FC, through HP StorageWorks 8/8 Base e-port
> > SAN Switch. Right now we only have this machine connect to the SAN
> through
> > switch, but we plan to add more machine to utilize this SAN system.
> >
> > Our application is apache version 1.3.41, mostly serving static HTML file
> +
> > few PHP. Note that, we have to downgrade to 1.3.41 due to our application
> > requirement. Apache is configured on has 500 MaxClients.
> >
> > The storage OCFS2 are formatted with mkfs.ocfs2 without any special
> option
> > on. It run directly from multipath'ed SAN storage without LVM or software
> > RAID. We mount OCFS2 with noatime, commit=15, and data=writeback (as well
> as
> > heartbeat=local). Our cluster.conf is like this
> >
> > cluster:
> >     node_count = 1
> >     name = mycluster
> >
> > node:
> >     ip_port = 7777
> >     ip_address = 203.123.123.123
> >     number = 1
> >     name = mycluster.mydomain.com
> >     cluster = mycluster
> >
> > (NOTE: Some details are neglected here, such as hostname and IP address).
> >
> > Periodically, we found that the file system work very slow. I think that
> it
> > happened once every few minutes. When the file system slow, httpd process
> > CPU utilization will goes much higher to about 50% or above. I tried to
> > debug this slow by creating a small script that periodically do
> >
> > strace -f dd if=/dev/zero of=/san/testfile bs=1k count=1
> >
> > And time the speed of dd, usually dd will finish within subsecond, but
> > periodically dd will be much slower to about 30-60 seconds. Strace output
> > show this.
> >
> >      0.000026 open("/san/testfile", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 1
> >     76.418696 rt_sigaction(SIGUSR1, NULL, {SIG_DFL, [], 0}, 8) = 0
> >
> > So I presume that this mean the open system call is periodically very
> slow.
> > I did about 5-10 tests which yield similar strace'd results (ranging from
> > just 5-7 seconds to 80 seconds).
> >
> > So my question is, what could be the cause of this slowness? How could I
> > debug this deeper? On which point should we optimize the file system?
> >
> > We are in the process of purchasing and adding more web servers to the
> > system and use reverse proxy to load balance between two servers. We just
> > want to make sure that this will not make situation worst.
>
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