-----Original Message----- From: redhat-list-bounces@xxxxxxxxxx [mailto:redhat-list-bounces@xxxxxxxxxx] On Behalf Of Yong Huang Sent: Monday, May 24, 2010 1:57 PM To: redhat-list@xxxxxxxxxx Subject: Re: Multipath I/O stats > Not nessacarily. If you advertise one 10 disk LUN from the SAN, > the OS will see it as one disk, and multipath can make multiple > paths to the same "disk". That's 10 spindles in one disk, which, > if they're fast or SSD, will saturate a fiber link. OK. I agree. Now a slightly different issue. Currently multipath load balance allows only one path to be used at any given moment, chosen in a round-robin fashion. Unless multiple paths are allowed to read simultaneously, the bottleneck is on the single path when the "disk" is faster. This makes "load balance" meaningless. If the "disk" is slower, even future implementation of multiple paths simultaneous read doesn't help in the sense of load balance because the bottleneck is on the "disk". Yong Huang ========== So are you saying that Multipath does not allow for multiple outstanding I/O request even if the underlying FC driver and such does? What happens if a large I/O request is made that will overlap between 2 LUNs? Is one I/O request sent to 1 LUN and when it completes then another is sent to the other LUN? ----- Jack Allen -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe https://www.redhat.com/mailman/listinfo/redhat-list
