A simple matter of…

I”m talking the 19″ wide variety that you put servers etc in. They seem to vary greatly in quality - unfortunately some customers seem to get really cheap and nasty ones.

First of all, some comments. There are two types of rack - comms rack and server racks. Comms rack are for network switches etc and only have bolt rails at the front. Server racks have bolt rails front and back. I”m only talking about server racks here.

Firstly, they have to be capable of taking quite some weight - they should therefore not flex if you try and wobble them. We’ve seen some that were so bad that when the server was slid in, the rack twisted so much that it pulled the slide rails apart!

Secondly, cables. You are going to have alot of cables at the back of the rack, so having a door that shuts immediately behind the server is a bad idea. In fact, at one customer this even prevented the rails from going in. So get a rack with a good 6″ of behind the rear bolt rails. Also, you are going to want to tie those cables to something, so you will want some hooks or something in the rack. Some racks just have bare metal - if you are lucky you might be able to use holes in the bolt rail, but then again, maybe not. Also, I like having cables tied to the side - away from the equipment so this isn’t satisifactory.

Those cables are going to have to come out of the rack, so you really want a nice large hole at the back rear of the rack so you can put cables through it. Ideally this hole will actually be open at the rear (i.e. an “n” shape not an “o” shape). You should also have front and/or rear stabilizers depending on how equipment is loaded - this will stop the rack tipping over. The racks should also be able to be bolted to neighbouring racks and have earthing cables that can be attached similarly.

Most racks don’t seem to be numbered at all - this is the height of cheapness IMO. We draw up rack diagrams showing where equipment is to be located. Having to count holes or markers is both error prone and a complete waste of time. It’s also quite hard if there is existing equipment.

PDUs - rack equipment should be using rack PDUs. This means both ends of the cables are “kettle-style” - one male, one female. They take up far, far less space and are the standard.

Power requirements are increasing every month - even today I can specify (within IBM spec) a rack of servers which requires 128A (64A x2 for redundancy). Rack space can be at a premium, so racks which accept PDUs into their side walls
I really like (yes, the rack is a bit wider, but having the PDUs at the side also keeps things substantially tidier).

Network cables - normally there an awful lot of these. The best method I’ve seen is to install right at the beginning patch panels at the top of the rack. A huge trunk of cables is installed up the left/right side of the rack (not blocking the bolt rails like one customer did) with a patch panel at the end using the top space in the rack.

If you require KVM switches, follow the same practice. Even better, do not buy lots of 1U servers, buy a BladeCenter - either from IBM, HP, Egenera or someone else. The savings in hassle alone is worth it - plus you save on the cost of cables, KVMs, switches and power.

Ventilation is critical now that machines use up so much power. Do not use glass doors, use well perforated doors. In fact, I hate doors, they get in the way when installing machines or looking after them - particularly in cramped datacenters - in fact in one case, a customer had a rack with the door wedged open past 90 degrees with a wall behind it so that you couldn’t close it - we needed to work in the neighbouring rack. So here is my idea - roller blind style doors. If you are worried about security, then you could use a cut-proof material (kevlar or maybe embedded wires?), also only make the roller just long enough (to prevent people reaching around the sides) and provide a lock. The roller could go from top to bottom (bottom to top would be a pain for installation - remember you want an “n” shaped hole in the bottom of the rack, not an “o” shaped
one). Alternatively it could go from one side of the rack to the other - it would probably take up less space than the hinges currently do on racks. These roller doors would probably cost less, definitely weigh less and most importantly remove all the hassle that I have with doors. For instance just the other day I wanted to compare two screens that were in adjacent racks - it was almost impossible because there was a rack door in the way.

Don’t forget to label the machines (front and back - it’s amazing how many times people lose track or pick the wrong box when walking around a rack). Also, please, please, please use double-sided velcro ties for all cabling - it’s so much nicer. I never want to see a single tie-wrap except for permanent features - and the only one I can think of is pre-installed network trunking as I’ve outlined earlier which is in the middle of the rack and basically there until the rack is finished with.