Hello all, 

we are about to configure a new storage system that utilizes the Nexenta OS 
with sparsely allocated ZVOLs. We wish to present 4TB of storage to a Linux 
system that has four NICs available to it. We are unsure whether to present one 
large ZVOL or four smaller ones to maximize the use of the NICs available to 
us. We have set rr_min_io to 100 which we have found offers a good level of 
performance. Though this raises an interesting question; that the 
multipath.conf man pages says that the rr_min_io parameter is the number of IOs 
across the whole path group before a switch is made to the next path. What 
constitutes a single IO operation ? A user opens a file for read access, one 
IOP to open the file, IOsX to read the contents, and another to close ? Do each 
of those SCSI operations happen on the same path ie. on the same block device ? 
If a second user comes along and requests data from the same block device do 
they happen on the same path or the next one in the path group ? We imagine 
that they will all happen on the same path until rr_min_io is reached and it 
switches over to the next path. 

We are trying to squeeze out the maximum performance from our system and we are 
unable to max out our 4 x 1Gbe interfaces. Any thoughts on how we can improve 
our performance ? 
Thanks, Phil 

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