Prevention of SPARC Enterprise M4000 Rail Kit Failures.

Asset ID:	1-73-1020275.1
Update Date:	2011-02-23
Keywords:

Solution Type FAB (standard) Sure

Solution 1020275.1 : Prevention of SPARC Enterprise M4000 Rail Kit Failures.

Impact

SPARC Enterprise M4000 Rail Kits are prone to failure at install time, causing the M4000 server to jam or drop as it slides along the rails in or out of the rack for the first time.

The slide mechanism of one or both rails can be damaged, and the server must be entirely removed from the rack and a rail kit must be replaced.

Contributing Factors

A SPARC Enterprise M4000 rail kit failure is more likely to occur when a mechanical lift is not used, when the installation is performed hastily, or when directions in the Equipment Rack Mounting Guide are not closely followed.

Symptoms

When the M4000 server is slid into the rack for the first time one or both inner ball bearing cars may catch and jam or drop bearings. Once the bearing car is damaged, the innermost rail (fixed to the server chassis) can slip out of the middle (fixed to the outermost rail, which is fastened to the rack. More ball bearings will fall out and there will be visible damage to the bearing car.

Root Cause

Unlike the M5000 rail kit which is entirely fitted to the rack before the M5000 chassis is lowered on to the extended rails, each side of the M4000 rail kit is delivered as two pieces. An inner rail, which is mounted to the M4000 chassis, and a middle and outer rail assembly, which is mounted to the rack.

When the server, fitted with the inner rails is mated (slid in) to the rail and bearing assembly, which is fastened to the rack, the alignment of the inner rails and the inner bearing car is critical. The middle and outer rail and bearing assembly which is fastened to the rack contains two items to ensure that the inner rail is well aligned as it slides into the middle rail bearing race; a clip exists which holds the bearing car fully forward, and a black plastic guide to catch and align inner rails as they and the server chassis slide into the middle and outer rail assembly FOR THE FIRST TIME.

As the server is first slid into the rack, the bearing car clip disengages allowing the inner and middle rails to slide past one another. After the initial mating of the inner and middle rails, the black plastic alignment guide remains, but the alignment and the full weight of the server is maintained and borne by the ball bearings in the inner bearing car.

If the bearing car is not clipped in the fully forward position, or the black plastic alignment guide is missing or damaged, the mass of the server can crumple the inner bearing car as the inner rail meets the first pair of bearings in the car. The bearing car will fail to hold each successive pair of bearings in alignment and the first insertion will feel tight or forced.

Documentation will be enhanced to describe the operation of the rail kit and to point out this failure mode.

Corrective Action

Workaround:

No workaround available - see Resolution section below.

Resolution:

Ensure that the middle to inner bearing cars are clipped in the fully forward position and that the black plastic alignment guides are intact before sliding the server into the rack for the first time.

Use a mechanical lift to support the weight of the server as it is first guided into the rack.

Note that if the initial alignment is off, and the installer has to back out and re-insert the server, that the bearing car may have come unclipped. Fully back out the server and re-inspect the bearing car clips and black plastic alignment guides before making a second attempt. A missing or damaged black plastic alignment guide can be overcome in the field by very precise positioning and the use of a mechanical lift. Any visible damage to the bearing car or clip mechanism will require that the rail kit be replaced.

Click through the images at...

http://uask4it.sfbay/~wm108421/opl/m4000rail/

...to better understand the operation of the rail kit, and precicely follow the rail kit to rack attachment instructions in the Equipment Rack Mounting Guide. Attachment of the M4000 rail kit to a rack with M6 pre-tapped holes, like the Sun Rack 1000, is fairly straight-forward. Attachment of the M4000 rail kit to a square hole rack like the Sun Rack II 1242 or Fujitsu and Fujitsu Siemens Computer racks is not. Be sure to read the square hole rack sections in the appropriate manual:

819-5367-13   Sun SPARC Enterprise Equipment Rack Mounting Guide

    hhttp://download.oracle.com/docs/cd/E19867-01/

C120-H016-09EN   FJ/FSC Sparc Enterprise Equipment Rack Mounting Guide

    http://www.fujitsu.com/downloads/SPARCE/manuals/sparc-commone/rackmount-en-09.pdf

Documentation will be enhanced to describe the operation of the rail kit and to point out this failure mode. In the mean time, pay attention to the existing Equipment Rack Mounting Guide and view these photos to better understand the operation of the M4000 rail kit.

819-5367-13 Sun SPARC Enterprise Equipment Rack Mounting Guide

    http://download.oracle.com/docs/cd/E19867-01/

C120-H016-09EN FJ/FSC Sparc Enterprise Equipment Rack Mounting Guide

    http://www.fujitsu.com/downloads/SPARCE/manuals/sparc-commone/rackmount-en-09.pdf

M4000 Slide Rail Operation

    http://uask4it.sfbay/~wm108421/opl/m4000rail/

The next version of Sun SPARC Enterprise M4000/M5000 Servers Product Notes will include this information;

http://download.oracle.com/docs/cd/E19855-01/
http://uask4it.sfbay/~wm108421/opl/Bearing_car-illos.gif
http://uask4it.sfbay/~wm108421/opl/126643.jpg

Identification of Affected Parts (how to):

Just prior to mating the rack mounted middle and outer rail assembly to the M4000 server mounted inner rail slides, check that the black plastic alignment guides exist...

http://uask4it.sfbay/~wm108421/opl/m4000rail/Images/4.jpg

..that the inner bearing cars are undamaged (pay particular attention to the first pair of bearings)...

http://uask4it.sfbay/~wm108421/opl/FF1RailFail/Images/7.jpg

...and that the inner bearing cars are clipped in the fully forward position.

http://uask4it.sfbay/~wm108421/opl/m4000rail/Images/10.jpg

Comments

The same M4000 rail kit is used in Sun, FJ, and FSC branded M4000s. It is shipped in the box with the server. Replacements are available through Sun via the following part numbers;

#371-0096      SPARE RACK MOUNT KIT M4000
F371-0096-02   FRU,FF1,KIT,RACK MOUNT

References:

BugID: 6797453
IBIS case: 70484988

      http://webhome2.eng/VSP_CAPE/cgi-bin/getcase.cgi?caseid=70484988

For information about FAB documents, its release processes, implementation strategies and billing information, go to the following URL:

http://tns.central/fab

For Sun Authorized Service Providers go to:

http://tns.central/SPE/fab/

In addition to the above you may email:

[email protected]

Internal Contributor/submitter
[email protected], [email protected]

Internal Eng Responsible Engineer
[email protected] Responsible Manager: [email protected]

Internal Services Knowledge Engineer
[email protected]

Internal Eng Business Unit Group
SSG ES (Enterprise Systems)

Internal Sun Alert & FAB Admin Info
18-Mar-2009: Completed draft and sent to Extended Review.
20-Mar-2009: No feedback from Ext Rvw - sending to Publish.

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