[PLUG] "server" quality components

[plug at merlot.com]

Carla Schroder (carla at bratgrrl.com) typed this ...
> There will be two standalone servers: one IMAP and one Apache web server. The 
> mailserver will have about 300 accounts. Not sure yet how much traffic is 
> expected for the Web server, or if it is going to be burdened with horrid 
> scripts or what. These are not quite mission-critical, maybe one step below 
> mission-critical.

What are the requirements for uptime, response time, expansion, time
before upgrading is reasonable/expected? How much downtime is allowed in
the event of a failure? How much planned downtime will  your customers
allow?

How much admin time have you allocated for these boxes and the services
running on them? Will they be in your facility or a colo?

You can buy uptime, but it's very expensive unless you have written
contract guaranteeing that you will be lucky. If you find the gods who
issue those contracts, let me know. #:)

You can run both email and web on one server and use drbd and heartbeat
to make the other a hot spare. Apply a 4x multiplier to your normal
admin time if you go this way.  Actually, I think it's close to n^2
where n is the number of services you're using heartbeat to fail over. I
started down this path about a year ago then went a lower-reliability
path to save my sanity. I couldn't afford that much uptime. #:)

The Google formula is to use so many cheap computers that when a few of
them fail, it doesn't affect you. Of course, they wrote their software
to facilitate this behavior and you may not have this option. And they
have teams of contractors sitting in their data centers rebuilding
failed systems 24/7, another cost you probably don't want to bear.

Bottom line: it's a balance, and I don't know enough about what you've
got on each side of the equation to make a detailed suggestion. Except
to say that my last pair of servers have dual LAN onboard, one 10/100
and 1 gigE. I used the gigE as a back net for communication between the
two, and it works VERY well. If they have to talk to each other (for
authentication? backups?), I suggest that you use a motherboard with
dual LAN ports like my Tyan S2099 (though I'm not a big Tyan fan, this
board works very well).

--Kurt
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