MSA1040/2040 Rack Mounting 19" rail depth adjustment range specs needed

[Aussie_Steve]

Gidday folks (edit 2 to fix typos)

Despite days of searching, I have not been able to find anywhere on the internet what the minimum and maximum distance between the outside mating surfaces of the front and rear mounting posts of a 19" rack can be for a MSA1040 and MSA2040. There are several "racking" instructions that merely show that once the front ears of the rack rail kit are attached to the front posts, slide the rails to suit the distance to the rear posts and tighten but it doesn't say anywhere what that adjustable range is? Even the online chat to so-called experts has drawn a blank. Surely someone must know or do people just buy these things and hope they fit?

For those not sure what I am referring to, in a 4-post 19" rack, there are a pair of "front" mounting posts that are mounted vertically 19 inches apart and a matching pair of "rear" mounting posts also mounted vertically 19 inches apart. The posts have square (or sometimes circular) holes punched in them and are usually labelled in groups of 3 holes. I group of 3 holes is called a "Unit". The height of the front panels will be sized in height with 3 mounting holes per 1 unit, so a 2U or 2 units high box would cover 6 mounting holes, a 3U is 9 holes and so on. The gap between the 1st and 2nd hole is the same as the gap between the 2nd and 3rd hole, but a smaller gap exists between the 3rd hole of a unit and the 1st hole of the next, so any 3 holes cannot be used as a Unit, rather fixed groups of 3 are defined by the smaller spaced gaps which are the end of 1 unit and the start of the next. Because of this, the holes are usually marked in groups of 3.

Some small rack mount items like switches only need to be mounted on the front posts and the chassis or body of the device hang behind in a cantilevered set-up with all the weight hanging off the front panel.

Heavy items or items that have a lot of depth like servers would place too much torsional strain on the front panel so rails are used as a sort of shelf, in most cases with the ability to slide in and out whilst supporting the weight of the item thus making for easy insertion/removal. The distance between the front and rear posts changes from rack to rack and some are fixed while others are adjustable but once items are installed changing the spacing is very difficult almost impossible without downing the equipment unless you want to risk hard disk damage. The rails may be able to adjust for a minimum distance of say 600mm out to a maximum of say 800mm but if your rack has say 550mm front to rear spacing, the rails will not be able to meet the front and rear posts because they cannot contract that far, likewise a 850mm rack would be too deep as the rails could not expand that far.

As an example, another server vendor lists their sliding rails for some of our servers as being:

Rail adjustability range (mm)
Square       Round      Threaded
Min  Max   Min  Max    Min  Max
631 868   617 861   631 883

The rack they are in has the front and rear posts 650mm apart so that server rail kit will fit.

Hence my question - it is crucial to know what the minimum and maximum adjustable depth of the mounting kit is in this case for a MSA1040/ MSA2040. I don't get why it is so hard to find and how the hell do other users buy a product without determining if it will fit? Other brands supply the adjustable range of the mounting kit in the standard installation specifications but not HP for some bizarre reason. HP head office say to contact a reseller but the resellers have no idea either!? Why is this essential parameter so elusive? or could it be that HP designers just assume everyone who buys their SANs also exclusively buys their racks too?.. which is not the case in the real world.

[Benjamin_Smith · Accepted solution]

Hi Steve,

The minimum and maximum ranges for the MSA 1040/2040 rail kit are

min: 635mm max: 936mm

To answer the question of how people know things will fit,  product depth is not defined by the EIA standard. However, two conventions for maximum product depth are in use in the marketplace and are defined by their markets.              

                     
The server market generally defines the maximum depth to be 25.5 inches, not including the product bezel. This depth is defined from the surface of the chassis mounting flange that interfaces with the rack column to the chassis back plane. This allows room for a cable management arm (CMA) to fit in the rack with the rear door closed. The most common and restrictive rack broadly in use is the Compaq 7000 series. For rail mounted products, an additional 2 inches is allowed due to the elimination of the CMA.                
                     
The telecommunication market generally defines the maximum depth to be 20".  

Therefore it can be safely assumed that any device which is intended to be racked in any of the HP 19" racks will by virtue of accepted convention, fit that of another vendor.  The exception would be if the 3rd party vendor themselves do not conform to these conventions.

In terms of finding such information, my advice would be to find a HP partner and ask them.  Partners have access to restricted HP services which are able to answer questions which are complex, undocumented or require in-depth escalation and analysis.  You can find partners HERE

Kind regards,

Benjamin Smith

Storage Presales
EG Office Based Presales EMEA

MASE  SSA v1

[Aussie_Steve]

Gidday Benjamin and thanks heaps for the bonser answer mate.

It's bizarre that such a simple question has been so elusive to answer. Other vendors publish documents explaining the min and max front to rear mounting rail distances some even detail the subtle distance variations between using square holes, round holes and mounting pins. Perhaps HP arrogantly assumes everyone who buys their computer equipment also uses their racks exclusively which we certainly don't. In fact, our racks have different front post to back post distances due to them being from different manufacturers and some have adjustable front to rear spacing that we have adjusted to best suit the gear in that rack. We have several items that fit in one rack but not another because the spacing of the rack posts is outside the adjustable range of some of the rack mount kits.

If I assume your dimensions are correct (afterall millimetres seem foreign to Americans heck most incorrectly spell the world standard of length as METER instead of the correct spelling that is METRE ) it means I can go ahead and order a MSA2040. If you're dimensions are wrong though, it'll be as useful as a one-legged man in a bum kicking contest.

I am disappointed though that the biggest 15k SFF drive I can buy for the 2040 is only 300Gb given other vendors are selling the 600Gb 15k SFF enterprise drives from Seagate and Toshiba. HP is only offering LFF drives in 600Gb but everyone is abandoning LFF in favour of SFF in enterprise grade equipment.

Cheers again for the response Benjamin. It's a bit early but Merry Christmas (yes we're allowed to say that down under where political correctness madness hasn't taken over). Hooroo bloke  (-:

[Aussie_Steve]

Well as luck would have it, I happened to know someone in the USA who bought a 2040 and got the min/max dimensions off them and they were very similar to the ones quoted above albeit in inches (the USA can put man on the moon but hasn't figured out metric works... what's going on there?) so I took the punt and ordered a MSA2040 for myself.

It has turned up a few days ago and I can confirm the adjustable rack range for distaances between the front and rear mounting posts are:

- 636mm minimum, 788 maximum with 3 screws locking the 2 sliding pieces ,or

- 940mm maximum if you want to risk using only 2 screws holding the front and rear brackets interlocked.

My rack has 650mm spacing so it worked out well with 3 screws per rsi.

A few quirky things about the MSA2040:

- there is no dress trim so it looks a bit cheap having the flexible circuit boards to the front ears and the metal work around the chassis visible from the front. A simple plastic escutcheon would have made added some class to it.

- unlike units from Equallogic and other makers that have lockable front covers, there is nothing to lock the drives in to protect from unauthorised removal of hard disks.

- there is a web browers based GUI that is very powerful and can control almost anything yet strangely cannot change the ports between FC and iSCSI ; you can only do that from the command line interface using the "set host-port-mode iSCSI" command yet the iSCSI parameters can all be set within the GUI.

If you are ordering a new SFF unit, be aware there is a new range of 2.5" drives available in 300Gb, 450Gb and 600Gb that run at 12Gb/s instead of the older 6Gb/s. The seem to built around the latest Seagate Savvio 15k.5 drives now marketed as Enterprise Performance drives...

The dual port drive part numbers are as follows:

HP MSA 600GB 12G SAS 15K SFF(2.5in) Dual Port Enterprise 3yr Warranty Hard Drive 

http://h30094.www3.hp.com/product/sku/11144145/mfg_partno/J9F42A

HP MSA 450GB 12G SAS 15K SFF(2.5in) Dual Port Enterprise 3yr Warranty Hard Drive 

http://h30094.www3.hp.com/product/sku/11144144/mfg_partno/J9F41A

HP MSA 300GB 12G SAS 15K SFF(2.5in) Dual Port Enterprise 3yr Warranty Hard Drive 

http://h30094.www3.hp.com/product/sku/11144140/mfg_partno/J9F40A