[Beowulf] No guards on 1u server fans - common practice?

Nifty Tom Mitchell niftyompi at niftyegg.com
Fri Mar 13 11:50:06 PDT 2009

On Fri, Mar 13, 2009 at 11:50:46AM +0000, stephen mulcahy wrote:
> I have inherited 40 servers which I'm currently building a Hadoop[1]  
> We ran into some fan problems after powering up some of the systems to  
> do initial smoke testing. After a little head-scratching and looking at  
> a system running on a workbench - it became obvious what was causing the  
> fans to fail. The SATA power cables and in some cases, the SATA data  
> cables were sticking into some of the fans blocking them. Hence the 
> error.
> The fans don't feature any guards (plastic or metal). I've since  

This is a common situation.

It pays to invest in a Tie-Wrap gun and a big bag of cable wraps.
A tiewrap Gun automatically tightens and cuts Tie Wraps flush with head
in one operation.   Adjust the cut off trigger to be gentle to not over
clamp the cables.  Inside the chassis small ties are better.

Also look for hook and loop ties for data and power cables outside of
the box.  I have found that the garden supply can sometimes have them for
less than computer stores.  I like the two or three meter roll where hooks
are on one side and loops are on another (i.e. no adhesive).   I cut them
into various lengths and like them because they are so handy in organizing
wires prior to using a tie-wrap for more permanent installation.

I especially like the hook and loop product for cables like infiniband
and coax where a too tight tie-wraps can mess with the cable quality.

In a repair shop you will see the tech snip the old wraps with diagonal cutters
replace the part and zip/snip reinstall the ties again.   There is a knack
involved to not cut the wires in how the nippers are oriented.

When you are shopping pick up a bag of multi colored ties and you can
quickly add a color pattern to both ends of a cable to make it easy to
find the other end.   I do this on most of my 'test' and 'temp' cables
it can be a lot quicker than colored tape.   This way I am less apt to
pull a production wire in error in a service situation.

	T o m  M i t c h e l l 
	Found me a new hat, now what?

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