[CentOS] Slow gfs performance

James Thompson james at ubercart.org
Mon Jun 9 12:09:27 UTC 2008

You don't mention it but I assume you are running on Fiber Channel not iSCSI? I am running GFS using CentOS 5.1 from two servers using iSCSI. I have Device Mapper Multipath setup so that makes my performance characteristics a little different but I have tuned the servers with the following commands:

gfs_tool settune <mountpoint> demotes_secs 600
gfs_tool settune <mountpoint> scand_secs 10
gfs_tool settune <mountpoint> statfs_slots 128

The first two I have set until 5.2 drops which will contain an additional GFS tuning parameter, glock_purge. Update 5 of CentOS 4 may already have the glock_purge parameter available. Run the command 'gfs_tool gettune <mountpoint>' and see if glock_purge is listed. It should be set to zero by default.

If it is there you can refer to this brief write up on tuning with glock_purge since you will not want to use the demote_secs and scand_secs settings I am using: http://open-sharedroot.org/Members/marc/blog/blog-on-gfs/glock-trimming-patch/?searchterm=glocks

Also, as a further note, your particular usage scenario will dictate what tunings are appropriate. I am not familiar with Oracle's usage of I/O but will both servers be accessing the same data on disk (particularly with regards to writing) at the same time?

-James Thompson  

----- Original Message -----
From: "lingu" <hicheerup at gmail.com>
To: centos at centos.org
Sent: Monday, June 9, 2008 4:54:44 AM GMT -05:00 US/Canada Eastern
Subject: [CentOS] Slow gfs performance


 Sorry for repeating same mail ,while composing that mail i mistakenly typed the send button.I am facing problem with my gfs and below is the  running setup. 

My setup 

Two node Cluster[only to create shared gfs file system] with manual fencing running on centos 4 update 5 for oracle apps. 

 Shared gfs partition are mounted on both the node[active-active] 

 Whenever i type df -h command it will take some delay to print my shared gfs partition,it is happening even if i continuously typing df -h command . Shared GFS file system storage is from IBM STORAGE.I don't know what parameter to be fine tuned,bcoz  of that may be i feel my  oracle apps is also very slow. 

In syslog i am getting following error continuously in one of the node 

less /var/log/messages 

test2 kernel: 493 [RAIDarray.mpp]AHA-SN01:1:0:10 Cmnd failed-retry the same path. vcmnd SN 7147770 pdev H2:C0: 
T0:L10 0x00/0x00/0x00 0x00020000 mpp_status:2 

 Any one help me to get rid of this slow gfs performance. 


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