On Tue, Mar 24, 2009 at 11:41:00PM -0400, John A. Sullivan III wrote: > > > Latency seems to be our key. If I can add only 20 micro-seconds of > > > latency from initiator and target each, that would be roughly 200 micro > > > seconds. That would almost triple the throughput from what we are > > > currently seeing. > > > > > > > Indeed :) > > > > > Unfortunately, I'm a bit ignorant of tweaking networks on opensolaris. > > > I can certainly learn but am I headed in the right direction or is this > > > direction of investigation misguided? Thanks - John > > > > > > > Low latency is the key for good (iSCSI) SAN performance, as it directly > > gives you more (possible) IOPS. > > > > Other option is to configure software/settings so that there are multiple > > outstanding IO's on the fly.. then you're not limited with the latency (so much). > > > > -- Pasi > <snip> > Ross has been of enormous help offline. Indeed, disabling jumbo packets > produced an almost 50% increase in single threaded throughput. We are > pretty well set although still a bit disappointed in the latency we are > seeing in opensolaris and have escalated to the vendor about addressing > it. > Ok. That's pretty big increase. Did you figure out why that happens? > The once piece which is still a mystery is why using four targets on > four separate interfaces striped with dmadm RAID0 does not produce an > aggregate of slightly less than four times the IOPS of a single target > on a single interface. This would not seem to be the out of order SCSI > command problem of multipath. One of life's great mysteries yet to be > revealed. Thanks again, all - John Hmm.. maybe the out-of-order problem happens at the target? It gets IO requests to nearby offsets from 4 different sessions and there's some kind of locking or so going on? Just guessing. -- Pasi -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
