Date: Wed, 12 May 1999 18:50:09 -0400 From: Mark Conway Wirt <mark@intrepid.net> To: GVB <gvbmail@tns.net>, freebsd-isp@FreeBSD.ORG Subject: Re: We are a growing ISP, need some advice! Message-ID: <19990512185009.J25726@intrepid.net> In-Reply-To: <4.1.19990512085152.00b757e0@abused.com>; from GVB on Wed, May 12, 1999 at 08:51:57AM -0700 References: <4.1.19990512085152.00b757e0@abused.com>
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On Wed, May 12, 1999 at 08:51:57AM -0700, GVB wrote:
>
> We have about 150 virtual domains running on the web server and about 800
> dialin accounts + the mail from all the virtual domains running off of that
> one mail server. We are starting to see a definite need for a bigger
> server farm. My question is, what should my growth point be from here, how
> do I scale this thing to accomidate all the users and domains I am hosting,
> because we are noticing the hardware starting to slow, the mail server
> actually hits swap space, even with 384 megs of RAM in it.
Web and Mail are both I/O intensive, so if you're seeing a slow down,
it's begin IO bound. 150 virtual domains and 800 dialin accounts should
be serviceable for a single computer.
IMHO, the first thing you would want to do is to split the mail and
Web onto different servers. In sizing the servers, don't scrimp
on the IO. A fast, caching RAID controller with striped or mirrored
partitions would do the trick.
>
> I have read up on doing round robin DNS with the Web Servers, but never
> really understood how the disks are synched up, does it run on NFS with one
> machine serving the content?
>
That's a big problem with round robin DNS. For the Web it works great
for static pages where you can replicate the sites, but dynamic sites
are a pain. Also, Round Robin DNS is only usually used for spreading
the load or a heavily hit site -- one that needs more than one server.
If your web server slows down, best to just move some of the sites
to a new server.
For mail, the standard way of doing it is over NFS, but
you'll need a good NFS server. See
http://www.earthlink.net/about/papers/mailarch.html
for a description of Earthlinks architecture. If you're thinking
about sharing NFS disks amongst multiple servers, you may want
to look at switching to something like qmail that allows for hashed
spool files, and Maildir format, which I've been told is a lot cleaner
in terms of locking over NFS.
That being said, I think with a well designed server, you should
be able to handle, say, 15,000 user's mail pretty easily.
--Mark
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