[Ocfs2-users] OCFS2 vs Oracle ASM CFS

[Sunil Mushran]

Jeremy Schneider wrote:
> Some quick questions for the ocfs2-users list, now that 11.2 is public. 
> (Now that it's public knowledge that Oracle developed a whole new
> [propriatery] cluster filesystem from the ground up for RAC.)
>
> 1) Seems that the 11.2 docs encourage using ACFS rather than OCFS2 for
> oracle binaries.  Would it be safe to say that OCFS2 isn't strategic at
> all anymore for Oracle database files?  I've also noticed that OCFS2 is
> the underlying filesystem in Oracle VM.  Is this a shift in strategy for
> OCFS2?  As a development team, are you guys increasing your focus on
> Oracle VM?  I wouldn't expect that Oracle would continue to invest in
> OCFS2 development only for the benefit of SLES...

OCFS2 was not developed for any one use case. It was always meant to be for
general purpose usage. While most of our early users were using it primarily
with the database, we have come a long way since then.

There is no shift in strategy. OCFS2 is still stress tested with the 
database
by multiple groups. As far as development effort goes, we took care of 
db usage
in our first release. In 1.0 we had support for directio, asyncio, 
extents and
large files. And the performance was in line with raw. Frankly, the database
does not expect much more than that from the file system.

In 1.4, we added unwritten extents that could one day be used by the 
database.
But mostly the new features were targeted towards general purpose usage.

The story will not change in 1.6.
http://oss.oracle.com/osswiki/OCFS2/Roadmap

Yes, OracleVM is an important user of OCFS2. So we are obviously focused 
on it.
But not at the expense of other users.

Oracle is not focused on OCFS2 for SLES. Novell takes care of that. 
Oracle is
focused on OCFS2 for EL.

> 2) I'm curious if anyone has tried running OCFS2 on DVM?  Would there be
> any point to using OCFS2 rather than ACFS?

I believe OCFS2 has been tested with ADVM. It works with one big caveat.
In OCFS2, we heartbeat in the fs itself. That is a problem if ADVM were to
freeze the ios temporarily for say resilvering. We intend to fix this 
issue by
dusting off the global heartbeat patches that allows users to specify a 
different
heartbeat device. Hopefully in 1.6.

> 3) ACFS shapshots -- or are those a feature of DVM?  Seems like a great
> feature - isn't xfs the only other currently released filesystem to
> support this?  Any plans to add snapshots to the OCFS2 roadmap?

No, XFS does not support snapshots. The only mainstream Linux fs to support
snapshots is BTRFS. (unlimited writable snapshots). Still not PROD though.
http://oss.oracle.com/projects/btrfs/

We have no current plans on supporting traditional volume based snapshots.
What we are working on instead is REFLINKs, which is inode-based writable
snapshots. I talked about it in the email announcing the 1.4.2 release.
http://oss.oracle.com/pipermail/ocfs2-announce/2009-June/000028.html

> This is why I've always loved OCFS2 so much to start with -- there is no
> "asm-users" or "asm-devel" mailing list.  :)
>
> -Jeremy
>
>
> http://download.oracle.com/docs/cd/E11882_01/server.112/e10500/asmfilesystem.htm