I've recently switched my SQL Server 2008 setup from iSCSI LUNs to VMDKs on NFS shares. I know some people had issues with this setup but it's working great for me.
The SMSQL snapshots are scheduled daily at 6pm and delete any backups older than 7 days. Usually this works fine, but once every few weeks the backup fails and I end up with a flexclone of my volume and an additional datastore mounted to the VM.
I looked into this today and saw that the backup from 08/10/2012 failed to delete a snapshot from over a month ago.
[18:14:13.027] DELETING BACKUP - [#1]
[18:14:13.027] Deleting snapshot copy sqlsnap__svmsql01_07-12-2012_12.00.37 of LUN D
[18:14:22.098] [SnapDrive Error]: Deletion of backup (sqlsnap__svmsql01_07-12-2012_12.00.37) failed. Reason: (The backup sqlsnap__svmsql01_07-12-2012_12.00.37 was not deleted successfully. Reason : The virtual entity ff6da25f-3297-41f5-9d03-dd50918c54b5 is mounted from backup sqlsnap__svmsql01_07-12-2012_12.00.37. Please unmount it and try again. ).
(SnapDrive Error Code: 0xc0041054)
I checked the NetApp, thinking there might be a stale and locked snapshot there, but that snapshot (sqlsnap__svmsql01_07-12-2012_12.00.37) doesn't exist.
I ran into this issue with one of my customers today and it resolved the problem, but the procedure was slightly different. I had to restart the VSC services and SnapDrive service on the SQL server a couple times before it took effect. Anyway, I am glad you got it working.