hi, there is no big difference in performance b/w dynamic and fixed disks.
"Dynamic is considered the best virtual disk format because it's easy to set up and offers the most flexibility. Still, it tends to use as much space as needed, resulting in a performance hit over time.
The fixed disk method is closest to what's common in the physical world. For example, if 250 Gbytes of space is being assigned to a select number of virtual machines, the downside would be in backup. All 250 Gbytes would be backed up even if only 50 gigabytes are in use, which leads to a lot of blank space being stored. "[/b]
This quote is from http://www.crn.com/software/199901716 and they are referring lun to lun backup in case of fixed disk. but if the backup is to tape, only 50gb (occupied space) will get backed up not whole 250 gb.
We like fixed size because it allows us to easily plan and manage our storage. With many hundreds of virtual machines and snapshots and then dynamic disks I think it would be a little overwhelming to keep track of the disk space. I am not sure it would be worth it for a little performance gain.
No, we don't. It just doesn't make sense for us. We liked the fixed disks and the predictability they bring. We are very strict about our disk allocation policy so we waste very little.