Dell racking question

coinstash

New Member
Mar 16, 2016
14
4
1
Brisbane
Anyone have an idea of an appropriate rack for Dell Precision gear? I have an R7910 and a couple of C4130s and all the racks I can find don't have enough depth to fit them.

I'll probably want a minimum of 12U height to allow for future expansion, since I have a shipload of X100 Phis to mount in them.
 

coinstash

New Member
Mar 16, 2016
14
4
1
Brisbane
Got to the bottom of this one myself. The approved Dell rack is called a Dell PowerEdge 2420 which is not visible on the secondhand market in Australia and in any case has been discontinued by Dell. The approved replacement is called an APC/Dell NetShelter SX 24U and those are available retail at OfficeWorks for AU$1772.00

A 24U rack is total overkill for my needs but there's nothing smaller that's usable with the required 1070mm depth. I did spot a brand new (unpacked but unused) NetShelter 24U on the market for AU$990 and it's just up the road but even that's a bit spendy. I'd expect a 12U rack to cost no more than $500 if it existed. It seems nobody caters for the home cluster market, might be a business opportunity for someone.
 

Terry Kennedy

Well-Known Member
Jun 25, 2015
1,060
500
113
New York City
www.glaver.org
Anyone have an idea of an appropriate rack for Dell Precision gear? I have an R7910 and a couple of C4130s and all the racks I can find don't have enough depth to fit them.
Do you need to have a door on the back of the rack? Bramhall's Marshmallow Theorem* predicted this problem over 35 years ago. When I run into this, I use rack offsets from Newton Instrument (we call 'em "knuckles") to extend the rear set of rails further back:





Newton catalog C.10 here - look on page 164 and following. You can extend by 3", 5", 7" or 8". Note that my pictures above are of a 23" rack, so in addition to the knuckles there are 23"-to-19" reducers.

You could also just decide to use a fixed mounting (no rails) - especially handy if you don't have rails for your chassis. Just mount the rack ears directly to the front of the chassis and support the rear on a horizontal bar (see page 168 of the Newton catalog linked above):



* The Marshmallow Theorem states that the volume of a marshmallow remains constant no matter what shape you force it into. When 1RU servers became a "thing", manufacturers started stretching the front-to-back distance to hold all of the stuff that used to fit in 2RU. IBM was one of the early leaders in this area, creating a 1RU server that was 45" deep and needed at least a 48" deep cabinet for mounting to allow for front and (mainly) rear clearances.

Extra points if you've ever heard of the Marshmallow Theorem and know where / who it came from. :cool:
 
  • Like
Reactions: nthu9280

ViciousXUSMC

Active Member
Nov 27, 2016
186
89
28
37
Those "knuckles" are not a bad idea for my rack question.

Been seeing lots of cheaper 15-20U servers without the depth for a dell (29")

Rather than get a 30" deep rack for one server with all my other equipment being shallow depth, why not extend just one spot for that server?
I'll have to track those down, and hope they are not very expensive.
 

Terry Kennedy

Well-Known Member
Jun 25, 2015
1,060
500
113
New York City
www.glaver.org
Rather than get a 30" deep rack for one server with all my other equipment being shallow depth, why not extend just one spot for that server?
I'll have to track those down, and hope they are not very expensive.
7" front-to-back, 2RU tall US list price is $20.25 here. Note that these are "telco" parts, which means:
  • They are "battleship gray"
  • They are made out of steel, not aluminum
  • They have threaded 12-24 holes
  • They don't have the center EIA hole, just the top and bottom
  • You may have clearance issues due to the (larger) distance between the holes and the edge
You can avoid the last 2 issues by using 2138640230, $32.47, but it is only a 5" extension.

The basic part numbering scheme at Newton is 004xxxyyzz for telco-style stuff, where xxx is the rest of a 4000-series part number, yy is the number of rack units high, and zz is the color code (30 is battleship gray). Other colors are Nortel brown, Lucent blue, etc. but are almost always special-order. EIA stuff is 21xxxxyyzz, same meaning as above.
 

coinstash

New Member
Mar 16, 2016
14
4
1
Brisbane
Do you need to have a door on the back of the rack? Bramhall's Marshmallow Theorem* predicted this problem over 35 years ago. When I run into this, I use rack offsets from Newton Instrument (we call 'em "knuckles") to extend the rear set of rails further back
I'm likely to buy another six C4130s so it would be best to find a rack that's deep enough. If I was only mounting the three units mentioned then this would have been a great idea.


Extra points if you've ever heard of the Marshmallow Theorem and know where / who it came from. :cool:
Heh. New one on me. :)