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.
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