Is there a way to connect/reconnect datastore on FC LUN to ESX in read-only mode ensuring that NO bit is changed in that LUN?
Some storage arrays have option to mark LUN as read-only but if array doesn't have such feture? Does ESX have such option?
In other words: after storage array failure I want to connect datastore again but I want to be sure that nothing will be changed on LUN that datastore is placed on. No signature, no filesystem - nothing.
I dont think that is possible, since the LUN is a DISK seen by ESXi and like you said, unless specified by the Array management as read-only.
However, you can have read-only datastore in NAS mounts.
if this is about a forensic investigation of that LUN here is a workaround - not sure if it would be clean enough to be used in court ... anyway this should work:
unmount the LUN
create new VM
attach the LUN as RDM
before starting the VM create a snapshot
boot the VM into a ESXi-LiveCD or into a Linux LiveCD with vmfs-fuse
even if that writes to the vmdk this changes would run into the snapshot only