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30 January 2007
A couple of months ago I changed job to be Project Manager for a number of European Data Centres. My new role now includes providing the facilities and cabling for our data centre customers. As a result I was forwarded details of a workshop being run by Black Box, earlier last week.
Here are a few notes that I've taken down from the workshop.
The Internal Standards for data centre cabling are:
TIA/EIA 942
prEN 50173-5
In all case this is for the logical design, and cabling rules, but does not cost the physical design of a data centre.
1Gb:
Cat 5e and above will all code with up to 100m
10Gb:
Cat 6 will go up to 37-55m (depending upon the environment)
Cat 6a will go up to 100m
Cat 7 will go up to 100m
The Cat 7 standard uses proprietary connectors, but it is recommended to use Cat 7 cabling with Cat 6a connectors.
At the desktop (or even most servers) it is not expected to need for than 1Gb, except in the very long term.
As an example a Hard Disk is only cable of handling 10-20Mb, and if processing is involved then this is unlikely to be over 1Gb.
| Multi-Mode Fibre | 100 Base FX | 1000 Base SX | 10000 Base SX |
|---|---|---|---|
| OM1 | 2km | 275m | 32m |
| OM2
| 2km | 550m | 82m |
| OM3 | 550m | 300m | |
| OM3e | 500m | 550m | |
| Single Mode | 1000 Base LX | 10000 Base LX | OS1 | 2km | 2km | 2km |
But as additional connectors are used it greatly reduces the distance that can be done. For example it could lose 100m of maximum distance by adding a single connector.
Based on the cost factor copper comes out well ahead of fibre unless the distances prevent copper being used.
As a general rule if going less than 100m then copper is preferred, between 100m and 550m then multi-mode fibre should be used, and over 550m then it will need to be single mode fibre.
In reality there are some other issues other than costs. These depend upon the environment and the number of cables required.
Category 6a and category 7 cables are very bulky, and if there are a large number of cables then the cable management within a standard patching frame is not realistic. This may need to a specialist larger frame, or consider thinner fibre cables, eg. a Black Box EDF frame.
Again due to the thickness of the cables the amount of space in large cable runs can be quite large. So if these are being run under the floor then the cabling could potentially effect the air flow under the floor and cause hot spots where the air flow is obstructed.
Although copper is very reliable fibre can have a better reliability. For example noise (external electrical noise) has no effect on fibre. Fibre is also crush resistant, whereas when standard copper cables are squashed the amount of interference increased. It is also possible to get high cutting resistant fibre.
Many of these issues sound a bit far fetched, and for some of these issues it will only be very large data centres, or very high density environments that would encounter them. The workshop certainly gave some things to be thinking about.
