I encounter an issues with Dell MD3820i (ISCSI) 10Gb SAN Storage, and it will always prompt Virtual Disk Not on Preferred Path Due to Failover and flash a red light in the SAN Storage
I did check my MPIO configuration in Windows 2008 R2 & 2012 R2, and noticed that 1 of the path will suddenly show Unavailable due to some unknown reason
We had log a case to DELL technical support for this issue, and they advise to put the Controller #1 to Offline Mode, and manually remove and insert back during non-peak hours
Manually put the Controller #1 in Offline Mode
Once we had manually remove and insert back, wait for few minutes and everything look working fine now
Verification on the Preferred Owner & Current Owner, it show both on the same controller now – Previously was Preferred Owner is Controller #1 , but Current owner is Controller #0
“Mpclaim –s –d” show all the path are Active
“dsmutil –g 0” show all the path are Active
We will continue to monitor this issues, and hopefully it will not happen again.