SAN Errors in the Hosts Tab in VirtuCache GUI
The SAN error count you see in the Hosts tab in VirtuCache GUI are errors VirtuCache encounters in the SAN IO path, most of these are from the appliance.
These are errors in the underlying storage transport layer (e.g. iSCSI), these could be compare and write errors if another host has acquired lock on a resource, transient IO errors, SCSI reservations if a host has issued a SCSI reservation on a resource and other hosts are not able to access it, timeouts, errors for commands that VMware issues that the SAN is not able to handle, etc.
Ignore these errors unless the errors reach .1% of the total requests / IO processed by SAN (shown in the same screen in VirtuCache).