Why hosts intermittenly lose connectivity to Dell datastore using fibre channel

Has this just started to occur, on a new implementation or old existing implementation?

- During a recent storage migration we notice that the moving from the EMC CX4 to the new Dell Compellent storage was exceedingly slow and failing.
- Upon investigation, frequent disconnect / reconnect of varying datastores on 1 cluster of 18 mixed ProLiant blades
- IORP trace key errors noted on the Dell storage
-Problem started about 1 month ago


Errors
1)Path selection policy path config: PSP VMW_PSP_RR doesn't support path configuration
2) Stat ssvc.vim.performancemanager: Basil write workload parameters for 276b76a0-c7cce24dace out of range oIO=0 isSizeBytes=575776
3) Solo.Envirnoment Browser: skipped 4 inaccessible datastores
4) Giving up device or resource busy error 195887105 opening SLOT file
5) Skipping device either due to VSI read error or abnormal state
6) Read ERROR Resource temporarily unavailable: file desc 85 returned -1 bytes
7) Some host is down need to reset the slot allocation

What make and model FC card are you using? Also what is the driver and firmware version? Also what build of ESXi 5.5 are you running?

could you please share snipped from vmkernel.log and vobd.log  when storage get disconnect so we can suggest you ?