On Thursday 05 May 2011 05:24:10 Marcelo Beckmann wrote:
2011/5/4 Nicolas Ross rossnick-lists@cybercat.ca:
Hi !
I have a server (Centos 5) that is using a pair of SAS drives to store the data. (Mail server) They are on an adaptec raid controler with a battery backup and write back cache active.
From time to time, I have sever peak io to those data disks (> 400 to 500
iops, > 70 to 100 megs/sec).
With iostat, I find that it's almost a write i/o problem. How can I find to which files the OS writes ? On OSX boxes, there is a utility called fs_usage that can reports any disk activity for a particular process or all processes. Is there any utility like this on Centos ?
iotop can points me to wich process, but that doesn't points me to what files are the culprits...
I sugest a look for tools like this http://freshmeat.net/projects/fsniper
it helps to make a script to watch file activities, and it uses a kernel feature
I discovered inotify some months ago when I looked into every initscript in init.d
[23:13:35 root@gw init.d]# cat /etc/redhat-release CentOS release 5.3 (Final) [23:13:45 root@gw init.d]# head restorecond #!/bin/sh # # restorecond: Daemon used to maintain path file context # # chkconfig: 2345 12 87 # description: restorecond uses inotify to look for creation of new files \ # listed in the /etc/selinux/restorecond.conf file, and restores the \ # correct security context.
more about inotify: http://linux.die.net/man/7/inotify
http://www.linuxjournal.com/article/8478 What Is inotify?
inotify is a file change notification system—a kernel feature that allows applications to request the monitoring of a set of files against a list of events. When the event occurs, the application is notified. To be useful, such a feature must be simple to use, lightweight with little overhead and flexible. It should be easy to add new watches and painless to receive notification of events.
If you go the inotify route, do keep in mind that you need to monitor for modify events, otherwise you would not see the file changes before the applications finish with the files.
Regards, Marian