[Beowulf] OS for 64 bit AMD

David Kewley kewley at gps.caltech.edu
Sat Apr 2 00:46:59 EST 2005

Thanks for your challenges, Joe.  Let me give you a bit of my background.

I am at this moment building a NAS server, and am working to enable and test 
xfs on RHEL4, for a ~8TB data volume.  I *want* to try xfs on RHEL4, and I 
hope to use it in production if I can satisfy myself that it's the right 

I get challenged by my colleages to justify straying from the default 
filesystem (ext3) that RH supports.  I hope to give them good reasons, 
because so far I like the feel of xfs (I have used it in a couple of other 
projects).  The final choice is mine, but I feel a responsibility to answer 
my colleagues' challenges.

The thread has gotten too tangled, so I'm going to drop most of it and make 
some short statements etc. instead.

You say xfsdump works, as if regular dump doesn't.  Dump *does* work.  What is 
so much better about xfsdump?

I'd really like to see comparisons of TODAY's xfs with TODAY's ext3, using 
whatever tests or comparisons you find most meaningful.  I'm not very 
interested in benchmarks or application tests from the past.  I am making a 
choice between xfs and ext3 today, not last year, and given that ext3 is 
claimed to have improved very recently, I want to see if those improvements 
change the balance.

Given my current work, I may have some (artificial) benchmarks in a week or 
so.  I would very much welcome suggestions about what to try, especially 
given yours (and other list members') expertise in this area.

RHEL4 beta versions were available for public download starting 9/27/04; 
interested parties could have started making detailed comparisons then.

Even though I wish xfs was supported in RHEL4, I'm not convinced that RH's 
choice *not* to support xfs is ill-considered or short-sightedly 
self-interested or done only out of competitive considerations.  I find the 
argument reasonable that RH chose to stick with ext3 because they believe it 
meets all their customers' needs, and they don't want to invest in talent to 
support other enterprise filesystems for major support-purchasing customers.

In particular, see this thread and its continuation in the October archives:


Even if you don't read anything else from this thread, check out these two 
posts from Arjan van de Ven, which quite forcefully presents his position on 
ext3 versus xfs:


If you believe he's misguided, argue with what he wrote. :)

> On a 2.6 kernel with CONFIG_LBD enabled, you
> can get up to a 9 million TB file on the same sized file system,
> though I would challenge you to gather, power, and connect sufficient
> number of disks to test this.

Yeah.  Let's see, that works out to around... <scribbles on 
envelope> ...400MW?  Yep, that's outside my budget.

> >>Note:  FC-x has xfs enabled, one only needs to use "linux xfs" on
> >> the boot line during installation.
> >
> > Yup.  They don't have to support it, which is likely why they don't
> > bother disabling it. :)
> Oddly enough, it works quite well in FC.  Imagine that.  They can
> have their cake and eat it too.  Without spending time/money/effort. 
> Other distros are doing it, and they are too in FC-x.
> Only they choose not to in RHEL4.  Obviously support has nothing to
> do with it (FC-x is a beta program for RHEL, and you need to fix your
> customers bug reports to make it a useful program).

How can you say, "Obviously support has nothing to do with it"?  I don't get 
that.  They have major customers buying expensive support for RHEL.  They 
offer no paid support for FC.  If they choose, they can ignore bug reports on 
FC xfs.


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