A Cabling Before/After:
by Jesse on Sep.04, 2008, under Best Practices, CableManagement
Anyone who knows me knows I’m a little insane when it comes to cabling.
Keeping cable management sane makes management, and troubleshooting easier.
The trouble of course is that usually, when you’re called in to do a clean-up, you’re not given the luxury of taking the datacenter off-line to do the work. Most of this was done online, though I had to shut-down a couple of single-attached linux servers in order to move their cables.
You don’t get the opportunity to truly clean up the environment when you can’t disconnect everything,however you can at least get the mess out of the way.
Before
After
Hidden cabling to the right of the switch
September 4th, 2008 on 8:46 pm
Much better. I hate cabling disasters.
One link to make you cry: http://royal.pingdom.com/?p=234
And another to make it all better: http://royal.pingdom.com/?p=240
September 4th, 2008 on 9:37 pm
One of the first gigs I got when I moved to Virginia was at the Library of Congress. There were two parts of the job.
* Switch migration (4 ED-1032′s –> 3 ED-64M’s)
* Cabling remediation
For close to 10 years, their solution to disconnecting hardware was to stuff the cables under the floor and leave them there.
What we pulled out from the floor was staggering. A pile of cables 4′ tall covering 9 floor tiles and a trash bin.
September 8th, 2008 on 11:02 am
Isn’t all cabling to/from a MDS switch supposed to come from the right so you can get the fan blade out without uncabling everything coming in from the left?
September 8th, 2008 on 11:07 am
Oi – can’t be proud of anything these days without someone chiming in raining on the parade.
It’s a good thought that I hadn’t noted – and something I’ll keep in mind going forward.
Luckily in this instance the cables are free-hanging excepting for the cable-guides, which are open and the cables are easily extricated from them. The bundes can be brought out and up without disconnecting to replace the fan-blade.
Pretty poor design if you ask me. It would have made more sense to have the fans come out the back. Especially given that the cable guides are provided by cisco for exactly this type of cable-management.
September 8th, 2008 on 12:20 pm
The only reason I noticed it was because I had multiple conversations the past few months with people here complaining as to how much they thought the EMC Connectrix cabinet sucked. They thought that the cables would enter from the rear get fed up through the middle tray (that has lots of sharp outer edges on the back) and then routed to the sides. When in reality it drops from the top, and the tray lets you route each switch down a down a different side across the front side to side (that has no sharp edges): i.e. the top switch drops from right, the bottom switch drops from the left, gets routed across the tray and drops down the other side. They couldn’t wrap their heads around it and decided to order me a new 4x post open rack that I did the exact same thing with and threw out the rack.
Agreed it’s a not a good design, it’s very counter-intuitive and rather annoying to bundle 96 strands of fibre off only one side.
September 8th, 2008 on 12:27 pm
He’s right. It won’t be a problem with the future devices(nexus), but for now, you need to always go to one side.
September 8th, 2008 on 12:28 pm
That said, I also use both sides, but cable them with slack so I can move the trays. It just looks better when you use both sides.
September 8th, 2008 on 11:25 pm
In the some-odd years the MDS95xx series have been out, I don’t think I’ve ever seen the fan blade replaced. Maybe that’s why it didn’t even occur to me that it needed to be accessable.
There really isn’t a good way to do it, especially with the over-subscribed 48 port blade (which I don’t like just on principle) the port density is so high that it’s almost impossible to have it not become a mess.
September 9th, 2008 on 12:22 pm
Where I work we have quite a few MDS9513s each with several fully populated 48 port blades. In the past this has created quite an over hang in front of lower blades!
I devised a model for flood-cabling the 48 port blades. Our structured cabling provider assembles 2 x 24-port patch panels with individual elements cut to just the right length (the cable to port 1 is longer than port 47). The fibres are all bundled together and protected with sleeving. The 9513 goes in one patch rack and the patch panels go in an adjacent rack where all the patching occurs (from left and right). The blade is only disturbed once, looks really neat and, more importantly, it’s supportable by EMC!
September 9th, 2008 on 12:50 pm
Yeah, I detest the 48. I like the 24, it still oversubscribes, but not by much, and very seldom will you see a port group at max….
I have seen trays die(usually just 1 or 2 fans) and have to be replaced. I don’t like the layout on the 6500/9500′s and I never will. It’s poor design.
September 9th, 2008 on 1:26 pm
Just remember the patch-panel rule. You lose .75db of light for every patch panel you go through. EMC will start questioning supportability at 3 patch panels, and at 4 you’re going to have very obvious problems.
The problem comes when you go through more than the recommended amount of patch-panels is, when idle the connection may look fine (though running a check on the SFP using the ‘FC’ command would be in order to get the actual receive levels on the Symm) When traffic starts moving, the laser spends more and more time in the ‘off’ state. through the wonders of modern physics, that means the average RMS of the light power drops dramatically. That will lead to flopping on the port and IO errors.
I don’t recommend more than two patch panels in an install. One at the storage/host end, and one at the switch end.
And always clean your optics. Preferably with a lint-free swab and alcohol. Believe me, it makes a difference.