Hello,<br><br>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.<br>
<br>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. <br><br>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<br>
<br>cluster:<br> node_count = 1<br> name = mycluster<br><br>node:<br> ip_port = 7777<br> ip_address = 203.123.123.123<br> number = 1<br> name = <a href="http://mycluster.mydomain.com">mycluster.mydomain.com</a><br>
cluster = mycluster<br><br>(NOTE: Some details are neglected here, such as hostname and IP address). <br><br>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<br>
<br>strace -f dd if=/dev/zero of=/san/testfile bs=1k count=1<br><br>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.<br>
<br> 0.000026 open("/san/testfile", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 1<br> 76.418696 rt_sigaction(SIGUSR1, NULL, {SIG_DFL, [], 0}, 8) = 0<br><br>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). <br>
<br>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?<br><br>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.<br>