LARGE single-system Cyrus installs?

[David Carter]

On Sat, 6 Oct 2007, Rob Mueller wrote:

> Are you comparing an "old" reiserfs partition with a "new" ext3 one where 
> you've just copied the email over to? If so, that's not a fair comparison.

No, a newly created partitions in both cases. Fragmented partitions are 
slower still of course.

> Give it a month or two of active use though (delivering new emails, 
> deleting old ones, etc), and everything starts getting fragmented again. 
> Then ext3 really started going to crap on us. Machines that had been 
> absolutely fine under reiserfs, the load just blew out to unuseable 
> under ext3.

We've only been using ext3 for about 3 months now, so I may still have
this to look forward to :).

> Talking with Chris Mason about this, data=journal is faster in certain 
> scenarios with lots of small files + fsyncs from different processes, 
> exactly the type of workload cyrus generates!

I can't see much difference on our Cyrus systems, but battery backed write 
cache on our RAID controllers probably masks a lot of the change. I agree 
that it theory it should make a very substantial difference.

> As it turns out, the memory leaks weren't critical, because the the 
> pages do seem to be reclaimed when needed, though it was annoying not 
> knowing exactly how much memory was really free/used.

Okay, I think that we had a different kernel memory bug.

We were running out of memory after 24 hours, and a 20 line test program 
could exhaust memory in seconds. This bug was in SLES four years back, and 
it was still there the last time that I looked (some months back now).

-- 
David Carter                             Email: David.Carter at ucs.cam.ac.uk
University Computing Service,            Phone: (01223) 334502
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