improving concurrency/performance

Jure Pečar pegasus at
Mon Nov 7 11:10:32 EST 2005

On Mon, 7 Nov 2005 09:00:08 -0500 (EST)
"John Madden" <jmadden at> wrote:

> The disks are quite fast.  bonnie++, for example, shows writes at over 300MB/s. 
> What I'm finding though is that the processes aren't ever pegging them out --
> nothing ever goes into iowait.  The bottleneck is elsewhere...

It's situations like this Dtrace was made for. But on linux we still have
to use some 'gut feeling' to figure it out ... 

So you say you have fast disks for bonnie, but still see slow imap copy
operations? What kind of SAN exactly do you have attached? Because fsync()
calls would still be my primary suspect here ... 

You say you're copying mail spool from one box to another via imap. Is the
source box able to provide mails at a fast enough rate?


Jure Pečar

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