As for MTA's I can't recommend QMail, sendmail, and postfix I can though. Exim also seems to be a contender. Again reiserfs seems to be king for spools. (lots of small files)
as far as your behaviour, it sounds normal for an i/o bound system, you can also watch vmstat output 'live' and watch for blocked processes.
--On Thursday, September 09, 2004 10:44 +0200 Marcin Owsiany <[EMAIL PROTECTED]> wrote:
On Thu, Sep 09, 2004 at 06:03:20AM +1000, Russell Coker wrote:You have to either be doing something very intensive or very wrong to need more than one server for 20K users. Last time I did this I got 250K users per server, and I believe that I could have easily doubled that if I was allowed to choose the hardware.
We have a little over 10K users, and the disk subsystem seems to be the bottleneck. When we reach about 600 read transactions + 150 write transactions per second (as reported by sar -b), the load average starts to grow expotentially instead of proportionally. There are about 20K sectors read, and 3K written per second. (That was before I turned noatime on. After that we had about 2K sector writes and 70 write transactions less, and load average dropped to a more sane value - about 3, instead of 20.)
More than 90% of the disk transactions are on the (logical) disk where mail is stored. The only processes which touch that disk, are qmail delivery processes (qmail handed mail by another SMTP-IN box: 0.8 local deliveries per second) and courierpop3d processes (7.2 logins per second).
We are using an "Intel SRCU42X" SCSI RAID controller, and the logical disk which caries mail is made of 3 Fujitsu 36GB 15K RPM disks.
Please tell me, what problem we are facing? Is the hardware so weak? Is it underperforming? Or maybe our load is exceptionally high? I can provide more statistics if they are needed.
Also, did you implement virus/spam scanning on that box?
kind regards,
Marcin -- Marcin Owsiany <[EMAIL PROTECTED]> http://marcin.owsiany.pl/ GnuPG: 1024D/60F41216 FE67 DA2D 0ACA FC5E 3F75 D6F6 3A0D 8AA0 60F4 1216
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