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SubjectRe: XFS and journalling filesystems
Date
>
>
>Andreas,
>
>Journalling slows everything down because it requires all writes (and reads)
>to be serialized. This decreases SMP parallelism. The last thing Linux
>needs is another slow SMP poor component. I think more is better, don't get
>me wrong. I jsut didn't like seeing some folks go belly up and start
>killing their internal projects (like ext3) just becuase XFS shows up on the
>scene. Particularly since it was a patently blatant predatory move by SGI
>based on pure politics -- so obvious. It's also just another unix file
>system, and comes with all the limitations of Unix FS's.
>
>Jeff

It depends on how you do (journalling sp??). XFS has an async log so meta data
operations get clumped into a single log write to disk (for several) ops (usually).
Most other journal FS' don't do this. In fact, the only one that does
async logging that I'm familiar with is XFS. I saw Stephen's design
doc and he talks about bundling up the meta data operations, too.

XFS does a really good job on SMP parallelism compared to other Operating
systems and file systems that I've seen. This is what it was designed for.
Parallelism/SMP issues must be done in cooperation with other OS
components (like a kernel_lock or lack thereof :-)). XFS on IRIX has lots
of nice fine-grained locks. This allows many threads to be working on
various things at the same time. I'm not sure how much of this will
survive the port to Linux, though.

From what I see, SGI is committed to Linux as one of their future OS'.
They are trying to make it better. The intent of releasing XFS is not
to squash other project, but to make Linux better (IMHO).

The XFS port of Linux will take lots of work and won't be a simple. It is
going to need lots of changes to fit and work well in Linux.

Back to code,

Jim

>
>
>----- Original Message -----
>From: Andreas Bogk <andreas@andreas.org>
>To: Jeff Merkey <jmerkey@timpanogas.com>
>Cc: <mcai7et2@stud.umist.ac.uk>; <linux-kernel@vger.rutgers.edu>
>Sent: Monday, May 24, 1999 8:57 AM
>Subject: Re: XFS and journalling filesystems
>
>
>> "Jeff Merkey" <jmerkey@timpanogas.com> writes:
>>
>> > much of it they are really going to give you. Another Unix File system
>> > (yawn yawn yawn) with journalling (which means it will be **SLOW**). I
>> > would vote for the ext3 project to continue. It appears they were
>reacting
>>
>> I'm using Linux for video applications. XFS has a very important
>> feature for video: guaranteed bandwidth. Also, journalling slows down
>> reading, but speeds up writing, which is again important for
>> video. So, as long as ext3 is not there, I'll be very happy about XFS.
>>
>> Andreas
>>
>> --
>> Reality is two's complement. See:
>> ftp://ftp.netcom.com/pub/hb/hbaker/hakmem/hacks.html#item154
>>
>
>
>-
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