Cannot remove Datastore because filesystem is busy

This error may appear when you are trying to unmount or delete VMFS.

There are few things that we need to keep in mind before unmounting datastore

Dumpfile

[root@HOSTB:~] esxcli system coredump file list
Path                                                                                                                Active  Configured        Size
------------------------------------------------------------------------------------------------------------------  ------  ----------  ----------
/vmfs/volumes/60992065-35330208-6275-78ac443ba554/vmkdump/4C4C4544-0052-5810-805A-CAC04F5A4233-3095396352.dumpfile    true        true  3095396352

# To remove the coredump file use command 
esxcli system coredump file remove --force

vsantrace

[root@HOSTB:~] lsof |grep vsantraced |grep volumes
[root@HOSTB:~]
# To remove the log, simply stop vsantraced, unmount the datastore and start it again:
~ # /etc/init.d/vsantraced stop
# Remove/Unmount Datastore
~ # /etc/init.d/vsantraced start
If you do not useVSAN you can also disable :
# chkconfig vsantraced off

Scratch 

From the advanced setting ScratchConfig.CurrentScratchLocation  (ESXi > Configure > System > Advanced System Settings) check if the ESxi host is used as Scratch Location .Edit the value ScratchConfig.ConfiguredScratchLocation and reboot the host.

Other

• No virtual machine, template, snapshot or mounted in VM CD/DVD image that point to the datastore
• Datastore is not used as a scratch location
• Datastore is not used as VMkernel Dump file locatio
• Datastore is not used as active vsantraced location
• Datastore is not used as Scratch
• Datastore is not used to store VM swap
• Datastore is not used for vSphere HA heartbeat
• Datastore is not a part of Storage I/O Control