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Re: ext3 + high load



Hi,

On Thu, Jan 17, 2002 at 11:04:05AM +0100, marko milovanovic wrote:
> hi everyone!
> does anyone know about ext3 having been used on very loaded servers (say 1
> billion mail per day as well as thousands of web pages served every
> seconds)?
> i'll be glad to know if it stands the load!

Inside Red Hat, we do exhaustive stress testing on all of our kernel
builds before they ever reach the public.  That involves things like
having 8-way SMP boxes with 8GB of memory pounding a series of
network, VM, CPU, filesystem and disk-level IO stress loads *in
parallel* for 3 days at a stretch.  That all gets done with ext3, and
we'll often get weeks of that testing done with up to a dozen test
machines at once on any given revision of ext3 before a big release if
there are a lot of changes involved.

As for the loads you are talking about... I doubt if you'll find any
Linux software anywhere capable of dealing with 11,000 emails per
second.  That's 11 per millisecond.  That's under 100 microseconds per
email *total* cost.  If you can find any single Unix host capable of
that, I'd be interested in seeing how they managed it. :-)  

The thousands-of-pages web load has been demonstrated under Linux (Tux
can do that easily enough), but that sort of load is mainly readonly
as far as the filesystem is concerned so both ext2 and ext3 should
cope OK.  Email is *heavily* write-intensive on the filesystem, and
includes a lot of synchronised IO operations (you can't ack an
incoming email until it's secured on disk).  I doubt any Linux
filesystem will give the performance you want for that, though it
might be interesting to try, and the 2.6 kernel may eventually have
the IO bandwidth to do it if you spread the load over a couple of
dozen disks.

The obstacle is more likely to be performance than reliability,
though.  ext3 should "stand the load", but whether any current Linux
disk-based filesystem can give the level of write performance needed
for 11,000 emails per second is doubtful at best!

Cheers, 
 Stephen





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