RE: MC/S vs multiple sessions
"John Hufferd" <[email protected]>
| Newsgroups | gmane.ietf.ips |
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| Message-ID | <39BA3BC178B4394DB184389E88A97F8CF2ACD5@hq-exch-1.corp.brocade.com> |
Because of I-T-L Nexus issues, most wedge drivers (such as MPIO) do not send I/O for the same LUN down different Sessions. Even if they do, they need to ensure that no I/O for the same LUN travels down another Session while I/O for that same LUN is pending on the first session. With Multiple Connections per Session (MC/S), there are no such restrictions. Therefore the Initiator can send commands for the same LUN down both connections at a rate that is only limited by the ability of the storage controller to handle it. It is also true that with MPIO commands for other LUs can occur on the other Paths, but this may or may not be the process which is most acceptable to the total environment. What this means is that performance is generally better with MC/S, but the degree of performance improvement will depend on the design of the Wedge Driver (MPIO) and the quantity of Multiple I/Os to the same LUN. . . . John L Hufferd Sr. Executive Director of Technology Brocade Communications Systems, Inc [email protected] Office Phone: (408) 333-5244; eFAX: (408) 904-4688 Alt Office Phone: (408) 997-6136; Cell: (408) 627-9606 ________________________________ From: Qi, Yanling [mailto:[email protected]] Sent: Wednesday, November 01, 2006 8:43 AM To: [email protected] Subject: [Ips] MC/S vs multiple sessions Assume my iSCSI target device has two network portals and my initiator device has two network portals as well. I could create two sessions or create one session with two connections between the initiator and target. I do have MPIO service on the initiator host that provides IO load balance cross the two sessions. I could not see the differences from the viewpoint of IO availability. Which implementation is better in term of IO performance? Thanks, Yanling Yanling Qi Engenio Storage Group - LSI Logic 512-794-3713 (Office) 512-794-3702 (Fax) [email protected] _______________________________________________ Ips mailing list [email protected] https://www1.ietf.org/mailman/listinfo/ips