Rackmounting questions

Rackmounting questions

Post by Bruce C. M » Thu, 06 Jul 2006 22:44:39

Hopefully someone here with more experience with rackmounting than I do
can answer these questions.

I'm considering purchasing a 19" server rack for home use to get my
various rackmount servers off the floor. The rack I'm interested in is
a 20U rack with 22" or 28" depth. The problem is, that I noticed rails
usually come in 20" and 26". Are these rails appropriate for these

I'm thinking I will go with the deeper rack because most Sun servers,
UPSes, and self-build server cases are greater than 22". It would be
nice, however, to save all of that space if I could get away with it.
Do you guys feel that 22" is too limiting? I currently do have one box
that is 26", a sun E420R, but I don't use it anyway and will probably
sell it soon.

Rackmounting questions

Post by Doug McInt » Thu, 06 Jul 2006 23:14:12

"Bruce C. Miller" < XXXX@XXXXX.COM > writes:

First off, *everybody* is different. Sun changes their mind quite a
bit over time too.

Sun's servers are among the shallowest in the bunch. Likewise, Sun's
rack cabinets are usually among the shallowest in the bunch as well.
What else are you wanting to rack-mount? How much extra space do you
want to provide for cable management?

The current x86 server depth is 29.5" rail to rail (front to back)
inside the cabinet. Accounting for power and some cable management,
about the bare minimum is thus around 36" deep cabinets, but this is
the minimum, and I also have 39" deep cabinets to allow for lots of
cable management and power options.

But it sounds like you are getting just the bare rack, so if you want
to pick up a current Dell or HP or something, you'd be looking at
having 29.5" deep rails.

The rack rails are two factors. One is that you need to get the ones
for that particular machine. They are all different. Two is to make
sure they are adjustable to fit your rack. The best option for
everything is to make sure your rails are adjustable somewhat. Most of
the current crop of x86 boxes are adjustable by an inch to an inch and
a half. Some of the older HP rails are the most flexible, not sure
what they are currently shipping, everybody's bringing in Dells now.

I've seen some of the cheaper 4-post rail only racks not even offering
setting the depth at 29.5", just 29" or 30", so having some of the
flexibility is a definate plus oftentimes. The Dells still work in
those, but something that is fixed depth often won't.

There's been alot of changes and whatnot in this area (ie. just go
back 6 years, and see what people were doing then. Pretty much 100%
change around, and servers have gone from 15-18" out to 28" deep), so
there's lots of things out there that might work, but current x86
servers are targeting that 29.5" rail depth...


Rackmounting questions

Post by Bruce C. M » Thu, 06 Jul 2006 23:37:12

oug McIntyre wrote:

To start off, I'm just mounting one 4U cisco switch, a 4U server that's
22" deep, and a shelf to put my Sun Ultra 5 on. Later, I'll be adding
at least another 4U box and a UPS. Probably not much more than that
though, since this is a home setup.

As for cables, I'm not sure I have enough to justify a special cable
management solution. So, at the moment, I wasn't going to do anything
in that regard.

I just wanted a plain, 4-post open-air rack, to save on costs. I
could've gone with 2-post as well, but I was hoping to put some sort of
flat surface on top of the 20U 4-post rack and put a monitor and small
keyboard there. Plus, I like the idea of mounting the servers on rails
so they aren't just stacked on top of each other.

More than 28" is a bit long for me. I was planning on having the rack
next to my computer room desk (I've put a lot of effort into replacing
fans and such to keep noise down). Plus, the selection for half height
racks is a bit limited anyway. There's going to be at least a few boxes
that are too long for me, and I'm ok with that. The only OEM rackmount
I think I'd want is a faster sparc box anyway. Anything in the x86
realm I'd rather build myself. From what you're saying though, I think
22" would be way too limiting.

In any case, my main concern is what rail size to buy for mounting
boxes on this 28" rack and whether the standard 26" rails will fit.


Rackmounting questions

Post by Doug McInt » Fri, 07 Jul 2006 04:14:39

"Bruce C. Miller" < XXXX@XXXXX.COM > writes:

The 2post racks usually need some additional bolting to the floor or
wall or something. The 4post racks usually can be self-standing.

But sounds like you have enough depth to do what you want, just
realize that you probably won't be fitting in any current x86 server
class boxes..

There is no "standard" rack rail system. They usually have to match up
with the thing being mounted unless you go for a very expensive
"universal" solution, or a shelf (or a sliding shelf).

Boxes of a certain class sometimes end up with the same holes and
such, but I've seen dozens if not hundreds of different rail kits for
rack mounting servers, and they are rarely compatible with one
another, and are a bear to retrofit.

The current crop of x86 machines are actually the most standard (the
29.5" deep, square hole/cagenut mount) compared to what has gone on in
the past.

The Cisco switch will just front mount easily enough. For that size,
probably everything else will be sitting on shelves unless you have
the rack-kit that goes with that server box ahead of time and can
verify it will fit in your rack that you eventually go with.