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MD3220i virtual disk preferred path error
I have an md3220i connected to two Dell r410 servers. The servers are in a Hyper-V failover cluster with two luns presented over iscsi.
There are 3 nics being used for iscsi each with its own subnet (6 subnets). Server one has two links to controller 0 and one to controller 1. Server two is the opposite with 2 to controller 1 and one to controller 0.
The problem is that after configuring iscsi with mpio I keep getting this error:
Virtual Disk not on preferred path due to AVT/RDAC failover
Somehow the two LUNs presented are switching controller ownership and throwing the error.
Is there anything I can do to fix this, or am I doing something wrong?
Dev Mgr
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December 15th, 2010 21:00
Did you install at least the host software from the MD Server CD/DVD? The native iSCSI multipathing isn't enough to work with an MD3220i.
Also; I'd suggest to either increase your iSCSI NIC count to 4 per server, or decrease it to 2 per server so that each server has the same number of connections to each controller. What you have may work, but in the dozens of setups I've done, I've never used an odd number (larger than 1) of NICs for iSCSI on an LSI (MD) or EMC SAN (on SANs that only use a single active controller at a time, it's a whole different story).
jadus01
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December 16th, 2010 06:00
Thanks for the response,
I have installed the MD3220i dsm driver for mpio. I haven't installed the full suite since this is Hyper-V Server 2008 R2, and it won't install. The MPIO driver is recognized correctly as far as I can tell.
I had 4 NICs dedicated for iscsi, but realized I need to have a private LAN between the two hosts for cluster communication and live migration, so I've direct connected the hosts using a single cable. I'll see if dropping to two NICs changes things.
To be clear, the device is working correctly, has correct paths listed in MPIO and correct volumes shown in disk management. It's just the warning about about preferred path thats bugging me.
jadus01
21 Posts
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December 16th, 2010 15:00
Ok, I believe I have this working, and you may be correct about the 3 nic's causing problems.
I have returned to 4 NIC for iscsi; two per host per controller.
With my updated understanding of how the MD3220i takes ownership of disks, I realize there will only ever be two NICs "active" in an MPIO state, which is ok now.
I just completed a live migration without fail, and without warning of disk ownership changing.
Now I just have to re-figure out how I'm going to store my VHD's and carve up the md3220i with this new found understanding.
Thanks!