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Planning May 14, 2009

Posted by jamesisaac in Uncategorized.

Now that the project is approved, it’s time to nail down the actual nuts and bolts of how the pieces are going to fit. We’re going to be installing a full 42U rack full of gear – internet and WAN routers, four switches, several VMWare host servers, and some non-virtualized physical servers, plus two SANs. The design goal for this project has been to identify failure points and work around them. For example, there will be two 48-port LAN switches to connect all the server LAN traffic together, and two 24-port SAN switches to connect the iSCSI network. We also have two SANs with a dedicated replication channel between them.

So, my big project at this point seems simple, but will have a lasting impact on the whole project: figure out how to cable everything together. I’m thinking of going with six colors of ethernet cabling, based on what is being carried by each cable:

  • LAN traffic to Switch A
  • LAN traffic to Switch B
  • iSCSI traffic to Switch C
  • iSCSI traffic to Switch D
  • internet-connected devices
  • KVM

I think I’ll go with red for internet and yellow for KVM. Then perhaps a light blue and dark blue for LAN and a light green and dark green for iSCSI. I just have this idea in my mind that I want to be able to look at a server and visually see that it has all the proper redundant cables plugged in, and then look at the switches and verify that they are all the right color and we’re not mixing traffic. It’s easier to think about this now rather than after everything is in place and there’s a rat’s nest behind the rack.

The other problem, though, is cable length. I have very little confidence in my ability to make custom-length cables – in my experience, it usually takes me three tries to come up with one RJ45 cable that tests out correctly. But we are talking about potentially 150+ cables, so I want to make sure that I don’t have extra loops dangling in the cage. I have the rack layout built, so the next exercise will be to estimate distance between each device and the switch it will plug into, and figure out if a combination of 3′ and 6′ cables will suffice. I’m just afraid causing the Flying Spaghetti Monster to spontaneously emerge from a mess o’ cables, waving his noodly appendages at my servers.



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