Multipath I/O stats

[Yong Huang]

> 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