Small Redundant web/mail setup
dwiest at vailsys.com
Mon Oct 23 20:03:21 UTC 2006
On Wed, Oct 18, 2006 at 11:57:04PM -0700, Ted Mittelstaedt wrote:
> ----- Original Message -----
> From: "Ian Lord" <mailing-lists at msdi.ca>
> To: <freebsd-questions at freebsd.org>
> Sent: Wednesday, October 18, 2006 5:34 AM
> Subject: Small Redundant web/mail setup
> > Hi,
> > I need to setup a high-availability setup for mail/web setup
> > I was thinking about the following setup:
> > 4 servers total:
> overkill, just asking for trouble.
> > Data Servers:
> > 1 Server holding all the websites data and mail messages. It
> > would serve these files via nfs to the application servers.
> > It would also run mysql
> > A second server Also sharing it's content via nfs,
> > replicating it's data though rsync each ?? minutes. The mysql would
> > run as a slave of the primary
> > Application Servers:
> > Both servers would be running apache, php, sendmail and
> > posfix and would serve content from the share nfs drive.
> > 1- Is this a viable solution, I mean by that, Is it Like this big ISP
> > are set up ?
> The really big ISP's use proprietary commercial clustering solutions
> that make multiple systems appear as one single system. We are talking
> hundreds of thousands to millions of users. We are not talking 5000
> users or fewer.
> You can easily serve 5K users on a single server. You just need to
> get good hardware. In other words, costs start at $5000 and go up.
> A lot of people are under the misconception that they can get several
> cheap $900 servers and assemble them into a redundant setup that is
> highly reliable.
> The real secret is in getting expensive name-brand hardware that
> doesen't go down. If you can afford that, your fine. If you can't,
> then you need to find a different table to play at.
Isn't part of the point in running a redundent configuration that you
can buy cheap(er) hardware? A $600 machine should be powerful enough
to handle that many users. Just make sure you are using RAID 1+0
filesystems, keep replacement parts on hand and are performing regular
backups. The real question to ask is what is the provider's SLA and
how much does an hour of downtime cost the provider.
In my experience, the only things to die on servers have been fans,
disks (really the motors), and the occasional power supply. The only
things a more expensive system may give you are additional power
supplies, hot-swap drive bays and multiple CPUs. Other than the system
board and possibly the processors, the server's components come from the
same sources as your commodity hardware.
I think the setup described above is viable, though I would consider
running the database (with master-slave replication) and application
services on the same server assuming it can handle the load. Also, you
can probably get away with using something like rsync to push changes to
your WWW servers. I'm not sure about email, but you could NFS export
your mail directories from a central server to the two application
servers. Just be aware of NFS' failure modes.
So, I'd go with two, user-facing systems and an administrative
system that receives email and possibly hosts your code repository.
If you can afford it, get systems with redundent power supplies and
hot-swap drive bays. Depending on your userbase, you may want to
consider a robotic tape library so you don't have to manually change
tapes. I've heard some talk of people using raw disks for backups, but
I don't have any experience with that type of setup.
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