Hi Charles, Thanks a lot for your answer... Of course, I was expecting a more hopeful answer. :-)
We noticed the problems stopping and starting the iSCSI services, too. We found out that you have to unload (or load) the kernel modules (involving iSCSI and multipath) in a very particular order: always the mpp driver (mppVhba, and only that one) first, then the iSCSI. Never touch the mppUpper, it will give you a kernel panic. Fortunately, except on one opportunity, never had problem with kernel panic happening when testing a failing path. So from that point of view we are "happy"; our problem is the speed. Thanks for sharing your experience. Andres. On 2009-08-25 09:40 , "Charles Riley" <[email protected]> wrote: > Hi, > > We evaluated an MD3000i a couple of weeks ago for a customer, and saw the same > poor performance that you do. Simply creating a 500GB ext3 filesystem took > nearly an hour (usually this takes minutes). > > Additionally, stopping and starting iscsi services (of course, stopping all > IO/unmounting iscsi luns first) would frequently result in a kernel panic. As > did pulling one network cable (simulated failing a path). The servers under > test were RHEL4 update 7. > > I worked with Dell's enterprise storage team for about three days on this > before the customer decided to pull the plug and send the unit back. In our > case the MD3ki was going to be used in a cluster, so not having multipath > available was obviously not an option. > > Charles Riley > eRAD, Inc. > > > ----- Original Message ----- > From: "Andres Plaza" <[email protected]> > To: [email protected] > Sent: Tuesday, August 25, 2009 9:23:20 AM GMT -05:00 US/Canada Eastern > Subject: MD3000i slow using multipath driver. > > > MD3000i slow using multipath driver. Hi! > > Im having a problem with a new MD3000i that we bought, and I was hoping that > someone can give me an idea or ³show me the light². :-) > > This is our initial setup: > > MD3000i: 2 NICs (4 ports), 2 subnets, everything connected and configured as > Dell suggests in their manuals (and verified by them). Using RAID 10. Latest > FW on the HDDs. > PE2950: RHEL AS 4.7; 2 NICs, 2 ports for the iSCSI (each one on a different > subnet). Installed the iscsi-initiator from RH, installed multipath driver > from Dell CD. > Network: GigabitEthernet > > Because we wanted (mainly) to write big files on the MD3000i, we tried > something simple for testing: > > dd if=/dev/zero of=test1 bs=4096 count=10000000 > > To create a ~40GB file. Surprise: it took more than 45 minutes! ~0.9 GB/m ... > Very slow, unusable for our needs. Let me put this problem to rest for a > second... > > Another problem that we wanted to tackle is to mount the same virtual disk in > two machines. For that, I choose to use GFS. I installed it on the PE2950, and > got the same performance as before (~0.9 GB/m). > > To test the clustering, I created a vm on a Dell R610 (using ESXii 4.0), using > 2 ports exclusively for the iSCSI subnet (so, like a real computer). That vm > is using CentOS 4.7, latest updates, default iscsi-initiator, GFS. > Simultaneously, I ran a similar dd commands (the only difference were the > filenames) in the PE2950 and the vm on the R610. Results: > > PE2950: ~0.9 GB/m > R610(vm): ~6 GB/m > > It¹s not a typo: the vm performed more than 6 times faster than the real > computer! Besides being a vm, the only difference in between the two OS is > that the vm did not have the multipath driver installed. So, to try it, I > installed that thing... And the performance went down to ~1.1 GB/m. So, it¹s > the multipath driver. > > Have anybody had a similar experience? Is anyone from Dell in this list, that > can comment in these findings and numbers? Has anyone used a different > multipath driver/system other than the provided by Dell? What your experience > on that? > > Thanks a lot! > > Andres. > > _______________________________________________ > Linux-PowerEdge mailing list > [email protected] > https://lists.us.dell.com/mailman/listinfo/linux-poweredge > Please read the FAQ at http://lists.us.dell.com/faq _______________________________________________ Linux-PowerEdge mailing list [email protected] https://lists.us.dell.com/mailman/listinfo/linux-poweredge Please read the FAQ at http://lists.us.dell.com/faq
