270 Management: System Interfaces
VSS attaches to the service and uses it to coordinate the creation of snapshot 
virtual disks on the storage array. VSS-initiated snapshot virtual disks can be 
triggered through backup tools, known as requestors. The VSS Provider 
Configuration Tool offers the following configuration options:
• Snapshot Repository Virtual Disk Properties—This section contains a 
drop-down list for the RAID level and a field for entering source virtual 
disk capacity percentage for snapshot repositories. 
• Snapshot Repository Virtual Disk Location—This section contains a list of 
preferences for the location of the snapshot repository virtual disk. These 
preferences are honored whenever conditions permit. 
The Microsoft VSS installer service for storage provisioning is available on the 
MD3600f resource media in the \windows\VDS_VSS directory.
  NOTE: When registering VSS during your Windows setup, the registration 
graphical user interface (GUI) prompts you to provide the name of your array 
because settings in the GUI are array-specific, not host-specific.
Storage management VSS hardware provider tips:
• The number of snapshot virtual disks that can be created using a single 
snapshot set varies with the I/O load on the RAID controller modules. 
Under little or no I/O load, the number of virtual disks in a snapshot set 
must be limited to 16. Under high I/O loads, the limit is 3. 
• The snapshot virtual disks created in the storage management software are 
differential snapshots. Plex snapshots are not supported. 
• Virtual disks to be used as source virtual disks for VSS snapshots must have 
names no longer than 16 characters. The VSS hardware provider uses the 
source virtual disk name as a prefix for the snapshot and repository virtual 
disk names. The resulting snapshot and repository names are too long if 
the source virtual disk name exceeds 16 characters. 
  NOTE: A volume is another term for virtual disk.
For more information on VDS and VSS, see microsoft.com.
book.book  Page 270  Friday, September 23, 2011  2:46 PM