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December 19th, 2011 12:00
iSCSI TCP Tuning - what are your best practices?
Google and these forums are full of tcp optimizing tips (i'm talking mainly windows here) for iSCSI connections. It seems to be more of importance on 10Gbit networks these days. However, i'm also reading alot of contradicting information, mainly because people mix and match networking terms like nagle, delayed acks, window scaling and some statements describing these settings are not necesary on some firmware levels etc. etc.
I was wondering which settings you use and have experience with. Which settings do good to your setup?
I use the only following:
- disabling delayed ack (TCPAckFrequency = 1) setting for iSCSI adapters in windows 2003 and up using generic nics for iSCSI traffic.
I'm reading up about a new setting in Windows 2008 for the iSCSI initiator called "iSCSIDisableNagle". It's in the EMC kb docs currently.
I cant figure out if this replaces the disabling of the delayed acks or if it's additional. I have not been able to test it either in my setup.
Anyone else got that one tested?
Looking forward to read about your tuning best practices. Please describe your experiences in performance gain if you can.
[i reposted this discussion after posting it earlier in the VNX forum, the VNX forum was a little quiet on the matter ]
Satish_Kutty
216 Posts
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January 3rd, 2012 09:00
Hi,
Please refer to the Primus article "emc156408" which explains the Best practices for iSCSI in detail.
Regards
Satish.N.Kutty
spgsitsupport
42 Posts
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January 3rd, 2012 09:00
Sadly this article does NOT answer the asked question!
Seb
kelleg
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4.5K Posts
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January 11th, 2012 14:00
See emc150702 - this is for the delayed ACK setting and yes, it is still active and required to improve Read performance.
There is a link in this article to emc234250 which provides some more information about the nagle algorithm. This is to help with VM's and clusters - this is in addition to the delayed ACK setting. There is a MS KB article linked to this article that provides more information about the problem with the nagle algorithm.
glen