VMware Lost access to volume on Brocade SAN switches

Earlier today I ran across the following errors in my ESXi logs:

Nov 15 08:03:10 esx02 Hostd: [6BA33B90 info 'Vimsvc.ha-eventmgr'] Event 305408 : Lost access to volume 51f7bd04-ace1a4c9-0114-0017a4770000 (LUN23) due to connectivity issues. Recovery attempt is in progress and outcome will be reported shortly.

It would always recover right away within 1 second and since I am on a Active/Active array it was not really an interruption.  It did bother me.  So I did some research and came up with fillwords.

The process as I understand it is that switches use these fillwords to setup link initialization.  Up until firmware 6.1 this was done by sending IDLE/IDLE messages.  Both sides would respond with IDLE this was specific to devices running 1G/2G/4G speeds.  Brocade then setup new fillword modes as show below:

Mode 0        Use IDLE in link init and IDLE as fill word
Mode 1        Use ARB in link init and ARB as fill word
Mode 2        Use IDLE in link init and ARB as fill word
Mode 3         Try mode 1 first; if it fails then try mode 2

You should set this mode as per your storage and server best practices.  I know that for my HP Blades using 8GB virtual connect it is critical to use Mode 3 which I was not using.  You can check you current config by logging into the switch and using this command:

portcfgshow port_number

And you can switch it via:

portcfgfillword <Port#> <Mode>

You can read a much better written article on that matter here.

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