iSCSi Immediate Data Option

piedthepiper
piedthepiper used Ask the Experts™
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Hi Guys,

We have been having some iSCSI replication issues, basically the speed has been really slow. But after working with Dell on the issue we enabled the Immediate Data feature and the speed shot right up.

I have been reading up on the feature, but cant seem to find a simple concise definition of what it actually does.

The idea I get is that it basically just forces data down the link, without waiting for a response?
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VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017
Commented:
see here

http://www.tcpipguide.com/free/t_TCPImmediateDataTransferPushFunction-2.htm

that's exactly what it does, sends the oustanding data....if that's what Dell recommends, it's clearly a tweak needed by their equipment, or works better with their equipment.

You have Jumbo Frames enabled also ?

Is this on the Software iSCSI initiator ? or hardware ?
piedthepiper

Author

Commented:
Hey Andrew

Thanks fro the link, it is what I was looking for!

Nah no Jumbo Frames all standard 1500 MTU and its hard ware iSCSI from SAN to SAN over a dedicated 1Gb link
piedthepiper

Author

Commented:
Pointed me to what I was looking for, I had trouble finding any concise info on it myself
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Fellow 2018
Expert of the Year 2017

Commented:
This is often the issue, that hardware hba's do not support Jumbo Frames.

In tests software hba and jumbo frames, performs better than hardware hba's without jumbo frames.
piedthepiper

Author

Commented:
I will bare that in mind for future reference

Cheers!

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