[Ocfs2-users] ocfs2 vs ext3?

[Joel Becker]

On Wed, Apr 29, 2009 at 05:24:11PM +1000, Andrew (Anything) wrote:
> > 	I just checked max-features, it doesn't include "local" which means 
> > that you still need to create dlm lock in your local node which will 
> > cost some delay. You can check whether your volume enable "local" by 
> > command
> > 
> > echo 'stats'|debugfs.ocfs2 /dev/sdX|grep "Incompat"
> > 
> > If the volume is mkfsed to used as local disk, you should see "local".
> > Otherwise you need to add "--fs-features=local" to your mkfs.

	Yeah, 'local' is a feature, but it's not a feature in any
default list because we generally expect to be used in a cluster :-)

> Thanks for your replies Tao and Thomas
> 
> I still intend on using the filesystem in a 3 node cluster, but when I found
> it to be 25x slower than a single ext3 part I thought id start
> troubleshooting at the start.
> 
> I just did a format of a small partition to give it a quick test anyway, and
> found that it performs just as well as ext3, in some test even better.
>
> Except if I understand correctly, local disables the ability for clustering
> completely?

	There are a lot of safety concerns we have to make just in case
there are other nodes in the cluster.  When in 'local' mode, those
checks are all disabled, and that's why we can run as fast as any other
local filesystem.  In a cluster mode, we have to have those checks
enabled, and it does cause a speed penalty.  But remember, you're
gaining the concurrent access on other nodes.  That's the tradeoff.  And
I think we compare favorably in speed to other cluster filesystems.

Joel

-- 

"We'd better get back, `cause it'll be dark soon,
 and they mostly come at night.  Mostly."

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127