Ocfs2 users - Dec 2009 - More questions: Max partition size? Throughput?

Thanks to everyone who answered my questions about OCFS2 and Linux
software RAID (http://www.mail-archive.com/ocfs2-users at
oss.oracle.com/msg03740.html).

In evaluating OCFS2 as a candidate for my application, I have a couple
more questions.

1) According to the FAQ
(http://oss.oracle.com/projects/ocfs2/dist/documentation/ocfs2_faq.html#LIMITS),
the size limit for a single OCFS2 partition is 16 TB.  The FAQ goes on
to say, "This block addressing limit will be relaxed in future
software. At that point the limit becomes addressing clusters of 1MB
each with 32 bits which leads to a 4PB file system."  Has this "future
software" been released?  If so, what version of OCFS2 and/or the
Linux kernel do I need?

2) Does anyone happen to know the maximum single-client read/write
throughput that has been observed using OCFS2, and what sort of
hardware was used?  For comparison, my current setup uses three
hardware RAID-5 chassis with 16 drives each, 4Gbit/sec fibre channel
connected to three controllers, and software RAID-0 to stripe across
the controllers.  Using XFS, I get sustained reads and writes of
700-800 MB/sec on files in the hundreds of gigabytes (i.e., these are
actual disk accesses, not cached).  I am talking about large, linear
reads and writes, of course :-).  And this is essentially what my
application is all about...  Should I expect significantly worse
single-client throughput from OCFS2?  Or is this a "who knows; just
try it" kind of question?

Thanks again.

 - Pat

On Wed, Dec 23, 2009 at 02:31:32PM -0800, Patrick J. LoPresti
wrote:
> 1) According to the FAQ
>
(http://oss.oracle.com/projects/ocfs2/dist/documentation/ocfs2_faq.html#LIMITS),
> the size limit for a single OCFS2 partition is 16 TB.  The FAQ goes on
> to say, "This block addressing limit will be relaxed in future
> software. At that point the limit becomes addressing clusters of 1MB
> each with 32 bits which leads to a 4PB file system."  Has this
"future
> software" been released?  If so, what version of OCFS2 and/or the
> Linux kernel do I need?
	Any version where ocfs2 uses jbd2 instead of jbd for
journaling.  This first appeared in Linux 2.6.27.  You also need a
recent enough ocfs2-tools to enable large journals (-J block64).

Joel

-- 

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