Starting with ESX 3.5 update5 VMware requires that the first 12 characters of a Virtual Volumes name be unique this is the Virtual Volumes serial number as seen by the ESX host (ESX 2.x and 3.5 prior to update5 did not use this and relied entirely on the LUN and Target numbers for any disk devices it discovered). Virtual Volumes whose names are not unique will be misidentified as duplicates of themselves and could result in some or none of them being discovered. For the same reasons VMwares Consolidated Backup Proxy also requires that the name of Virtual Volumes mapped to all ESX Hosts, be unique, however this software requires the first 8 characters not 12. Therefore for configurations with a mix of ESX and VCB you should make the first 8 characters unique to meet all requirements
