Mike, that is a very good point. I will adjust the session queue depth first to give this a try.
Thanks, Frank On Tue, Aug 3, 2010 at 3:03 PM, Mike Christie <[email protected]> wrote: > On 08/03/2010 09:12 AM, Frank Jansen wrote: >> >> Hi, >> >> During the testing that I am doing, I run into a bottleneck when I run >> I/O to more than 1 device at the same time. >> >> In my current test configuration, I have the following setup: >> >> Target server has MegaRaid with 2 RAID 1E devices, which are mapped >> through lvm into large and small LUNs. 4 LUNs are made available for >> each RAID 1E devices through 2 instances of tgtd. Small LUNs are on >> control-port 0 and large LUNs on control-port 1, which are mapped to >> separate nic ports (10GbE each). >> >> Initiator server had no problem discovery each of the portals and is >> running I/O to 1 large LUN and 1 small LUN, which should separate all >> traffic. I'm using iozone to generate the traffic on both LUNs. >> >> What I am seeing is that I/O starts on 1 LUN and appears to wait until >> the data file has been completely written and read on that LUN before >> starting on the next. Is it possible that this is really happening in >> this manner? >> > > It is possible. It depends on the order that the block and scsi layer sends > the IO. If the device and session q depth is 16 and the block layer sends 16 > requests then it will all go to the one device and one device will sit idle > until IO starts to complete. There scsi layer will check if devices could be > starved and so when those commands complete it will make sure the next > device is used first. > > You can either: > 1. Make sure the device's queue depth is lower than the session q depth so > that IO can be sent to all devices at the same time. > 2. Do a target per lun. > -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en.
