> From: William T Wilson <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Subject: Re: Advice for 4000 mail users on a Red Hat 5.0 box
> Date: Friday, May 15, 1998 4:09 PM
>
> On Fri, 15 May 1998, Peter Chen wrote:
>
> > Exchange Server 5.5. But I manage to persuade the management to use Red
Hat
> > Linux 5.5 instead.
> >
> > - Now am I too ambitious?
>
> You bet you are. 5.5 isn't even out yet. :)
Sorry, my typo. It should be RH5.0.
>
> > - Can a Red Hat Linux box handle the load of a heavy mail server
serving
> > 4000+ clients?
>
> Yes, assuming that the hardware is up to the job. NT certainly won't do
> it. (Well, it might, but I wouldn't bet my job on it)
>
> > - Can a stock Red Hat 5.0 sendmail 8.8.7 handle so many users, for
> > example, more than 2000 concurrent SMTP connections? Or should I
recompile
> > the sendmail?
>
> There's no fundamental limits that I'm aware of in the Red Hat sendmail;
> it's the same sendmail that the rest of the world uses. However, qmail
is
> faster than sendmail, so you might want to look into that.
I can't find a qmail SRPM or RPM package. Moreover, since I don't have much
experience with qmail, I don't want to lose my job and Linux's reputation
as well. But I might switch to qmail after the mail server is up and
running.
>
> Are you really going to have 2000 concurrent SMTP connections? Unless
> your users do nothing but send mail, your 4000 users should never
generate
> 2000 SMTP connections. I'm assuming your incoming mail behaves in a
> reasonable fashion as well (i.e. doesn't come in enormous bursts).
>
We have a Sun Enterprise 5000 web server that sent several thousands of
mail inquiries in a burst. I am afraid the Linux sendmail server might be
swarmed. I personally saw that there were more than 2000 open sendmail
sessions on the Sun server by doing a "ps -ef | grep sendmail | wc". Is
this possible for Linux kernel 2.0.33/24 or the stock sendmail in RH5.0?
> How are your users getting their mail? Are they getting it from POP/IMAP
> from this same server, or is this server just a big hub and delivering
> their mail via SMTP directly to their personal machines? My guess is the
> former. In that case, handling the POP requests will probably be more
> trouble than the SMTP requests.
Yes, you guessed it. All 4000+ mailboxes will be on the same server. Is
this realistic for RH5.0? Can /var/spool/mail directory contain so many
files (mailboxes)? If not, what is the best way to place the mailboxes?
>
> > - Should I patch kernel 2.0.33 with file-descriptor patch and
recompile a
> > new kernel?
>
> Wouldn't hurt. You should get the 2.0.34 kernel in any case.
Is 2.0.34 released. I heard 2.0.29 is more stable then 2.0.30-33 under
heavy load. Has 2.0.34 fixed the problem with 2.0.30-33?
>
> > - Can a Pentium II 233Mhz, Intel 440LX chipset, 256MB RAM, Asustek
SC875
> > UW SCSI controller, two IBM Ultrastar 9GB UW SCSI hard disks do the
job?
>
> I'm not familiar with that SCSI controller.
It is using the NCR 53c875 UW controller. Heard that it is cheap and has
good driver support.
> Be sure you set RAID
> (striping) on the drives,
What do you recommend, hardware or software raid? If hardware raid is
recommended, which raid controller is best in terms of support and
performance?
> and you will have to add some RAM if you're
> really going to have 2,000 concurrent connections. How much is in the
> Solaris system that your ISP is using? If you have only 4,000 users, you
> should probably not count on more than a hundred or so simultaneous
> connections at the very most and 256M should be enough. What you need to
> serve the POP/IMAP is another concern. Do all your users come in in the
> morning and all check their mail at once?
Yes, can't rule that out. So if both sendmail and POP/IMAP server are
running, is 256MB sufficient? Or should I go for 512MB to play safe?
> In which case you might have
> perhaps not 2,000 but likely a couple hundred outstanding POP clients,
> perhaps; you might want to go to 512M of RAM.
So you recommend 512MB of RAM for a couple hundred outstanding POP clients?
> If on the other hand they
> don't all do this but check their email at a more leisurely pace, then
> your system as it stands should be fine.
>
>
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