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February 13th, 2012 16:00
Equallogic iSCSI Flowcontrol
Hi. I have a multi-tiered Equallogic SAN where the server (blade) access switches are Dell M6220s and the tray side access switches are Dell PC6248s. Access switches aggregate to a common distribution - Nexus 7018. Jumbo frames are enabled on access and distribution tiers. Flowcontrol is only enabled on the access switches. Is it also a requirement to have flowcontrol enabled on the distribution tier?
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rogerharrell
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February 14th, 2012 06:00
Thank you Joe. So on the distribution flowcontrol should be enabled as "receive on" or "transmit on" as well?
DELL-Joe S
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February 14th, 2012 06:00
"Receive on" should be all that is required.
-joe
DELL-Joe S
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February 14th, 2012 06:00
From the host to the array, flowcontrol should be end-to-end. So if the distribution tier is passing iSCSI traffic between the host and array, yes, it should be enabled.
-joe
Tonkie67
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June 15th, 2012 21:00
Although in the answers it is advised to enable flow control, and if doing so it has to be enabled end-to-end: I do see that you have PCT62xx switches in the setup. For flow control to work good the switches do need buffering capacity (so they can buffer some data when one end can't handle the rate of incoming data and thus sending a pause frame to hold off data) and the PCT62xx series is lacking (much/usable) buffering capacity.
As member of the Dell networking support team in EMEA we have found that it can be better NOT to use flow-control when PCT62xx is involved in an iSCSI environment: but testing what is best in your specific setup is the best way to find out.