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Re: ZMailer "hangs up" on message queues...

  Folks,  I am traveling, and will continue to do so until next weekend.
Catching up my email is whole other adventure...

On Thu, Jul 26, 2001 at 09:39:58AM +0200, Arnt Gulbrandsen wrote:
> Michael Loftis <mike@activemessage.com>
> > CAllign a fork would be more expensive than anything else, we're needing
> > a *minumim* 40 messages/sec, with a target of about 80 messages/sec. 
> That's a serious amount of mail - what hardware are you using? In
> particular, what's your spool disk? I suspect that the spool disk is going
> to make more difference than any number of system calls.

   A hard limit for system performance comes from the speed of
Directory Operations (rename, link, unlink, open) that your system can handle.

Most UNIX filesystems have limitations due to synchronous nature of the
updates of the directory metadata.  Say:  5 ms for disk read/write, read+write
for  anything that modifies the directory (or two reads+writes), plus what
datafile gets committed.

Faster performances are available at filesystems using journaling/logging.

Also having lots of disks in parallel stripes will increase the number of
heads that can be moving at the same time, thus speeding up (statistically)
the disk accesses.   (RAID1 + RAID0 is my recepie)

Going faster will in the end translate into database TPC benchmark.
Think of it;  now we use the directory system for database index with files
as data content for each index.   Things can be done differently.
(And have been done repeatedly, although not with ZMailer, I think.)

> --Arnt
/Matti Aarnio	<mea@nic.funet.fi>
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