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42378
September 12th, 2013 02:00
Fiber or copper?
I am looking to purchase two Compellent SAN's and wondered if anyone had a preference for fiber or copper for connectivity. The SAN's will primarily be used for Vmware and also SQL data. Some of my hosts already have 10gb NIC's so using copper would mean I wouldn't have to purchase so many HBA's, but that is the only think swinging the decision at the moment. I have read that you will see more latency over a copper connection than a fiber. Any thoughts would be appreciated.
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Dev Mgr
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9.3K Posts
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September 13th, 2013 07:00
50 meters should be doable with copper, but at that distance I'd suggest to start considering optical cables.
Will there be (iSCSI) switches in both server rooms? If so you could do copper (cheaper cables) and get an IO module for each side with optical ports to link the 2 rooms together.
Dev Mgr
4 Operator
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9.3K Posts
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September 12th, 2013 09:00
Do you mean fibre channel vs iSCSI, or do you mean optical iSCSI vs copper iSCSI?
DELL-Kenny K
685 Posts
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September 12th, 2013 11:00
When deciding between the Fiber and the iSCSI you could see some issues if for example the you are running a 4GB rate cable on a 10GB rated card. However if you are using the properly rated cables and cards then you will likely not see any difference in latency between the two different arrays. It will also depend on the transport layer and the setup of the network and the distance of the SAN, servers, and switches. I hope this helps, feel free to let me know if you have any further questions or concerns.
fluffy998
12 Posts
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September 13th, 2013 02:00
Hello,
We are looking t optical iSCSI and copper iSCSI. The two server rooms are about 50m apart and we are looking at the powerconnect 8132 or 8132F switches and just deciding which ones will be best.
fluffy998
12 Posts
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September 13th, 2013 08:00
Yes we are planning two switches for each SAN in each server room. Copper for the hosts and fiber between the two rooms sounds good.
trichert
15 Posts
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October 11th, 2013 07:00
Kenny,
I disagree with you. There is a huge difference in latency between iSCSI and FC. FC has a base latency between 2 ports on a 3m cable of 50microseconds. iSCSI over the same connection is around 400-500.
This makes no difference for file servers but if you are going to put SQL or Exchange on it, FC is much lower latency and also does not have to deal with OSI stack issues such as collisions and retransmits.
iSCSI exists because it is simple, but if you are at all concerned about performance you need to look at FC. Hopefully soon Compellent will support FCoE which will give a true 'networking' side of the house solution comparable to FC without OSI issues.
mtanen
118 Posts
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October 11th, 2013 19:00
Compellent supports FCOE...