[Seattle-SAGE] Server room build questions

Scott McDermott scottm at octaldream.com
Wed Apr 27 17:26:00 PDT 2005

Paul English wrote:
> So on to the questions:
> Given a commercial office space, does a roof-mounted AC make the most 
> sense?

We have ours in the computer room, but I wouldn't make this call off handed.
There's a lot of variables that'll affect what makes the most sense for your
environment, including what local building codes require. I would definitely
talk to a good air conditioning company to help you with this (for my 2
cents I'll recommend Pacific Air, they have some very good people and I've
been very happy with them.)

> What are people's feelings on raised floors vs. tiles/anti-static carpet? 
> I'm very opposed to running network/kvm cables under floors (give me a 
> ladder rack any day), but raised floors can be handy for routing AC to the 
> front of the racks and running fat trip-causing power cables. 

I say ditch the raised floors. Since cold air falls, (presuming the rest of
the space allows the option), you can have vents in the ceiling in front
your racks and you'll do fine. And adding raised floors to a space that
doesn't already have raised floors will certainly not be worth it!

> How much AC should I spec - get the maximum capacity 20 rack's worth now, 
> or get a lesser amount now and plan to upgrade? 

Figure out how many BTU your equipment generates per hour and feed it to
your AC company, letting them know your projected growth and let them help
you make an intelligent decision.

> Should I spec out a backup AC? Or just plan on shutting down all of the 
> non-critical systems in the event of an AC failure. 

Will your non-critical systems shut themselves down if the AC goes at at
2am? Will your computer room be 110 degrees when someone finally shows up to
the office? Will the non-critical systems have weathered it without a hitch
and the critical systems failed horribly leaving you to discover that your
backups aren't quite as good as you thought? (Not that I'm bitter...)
Seriously, though, this is more of a cost/benefit issue, and will depend on
how many tons of cooling you need and how much money/space you want to
devote to it. We have a backup cooling system now, and we also have a
netbotz monitoring the environment that starts paging people if it gets
warm. That said, if you have a good quality AC system, you probably won't
have any issues. (The one we had fail did not fail in this category.)

> How much power should I spec? On this one I'm fairly sure that I should 
> probably spec the full 20 rack's worth (200A?) and just get the breaker 
> panel put into the room with circuits sufficient for 6 racks. 

I really like the APC ISX system, myself. In fact, I can't recommend it
highly enough, myself. (Though I'm told you should stay away from the
managed power strips that let you remotely power equipment off. I have no
experience with those units myself, but have heard complaints about them
from at least two people, though one said the problems seem to be fixed with
the newer units.)

You can buy the ISX for your needs today, and grow it over time with
additional modules to increase capacity and runtime. It's not necessarily
the cheapest solution up front, but it'll certainly be cheaper than buying
everything you need for the future now. I also think it has more life in it
than your usual UPS system. Mark Machkatel at AC Power in Redmond has worked
with several SSG people before (some with requirements that make yours and
mine trivial) and can help you with this part of your datacenter.

> What are the considerations for a backup generator vs large (Liebert?) 
> UPS? I'm leaning towards an auto-start generator right now, with small 
> rack-mount UPSen on the 24/7 critical systems. 

You should have a UPS on all your systems, even if it's only for short
runtime. That'll protect your equipment while the generator kicks in. Either
that or a really large UPS. That's sort of a balance you have to find
between cost, hassle, and how many power outages the area your in has.

> Do we bother with a fancy dry fire supression system? Seems like a major 
> PITA and would take a big chunk out of the budget for everything else. 

I recommend against the dry suppression systems. Look into fine mist water
systems. I can't say how they compare in price to dry systems, but they are
not a hazard to humans and will do less damage to your computer systems. All
you'll need to do is dry your systems out and fire (ha!) them back up. With
the dry systems you'll actually have to have your systems cleaned...

Scott McDermott

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