Understanding SnapManager support for volume mount points

This topic describes SnapManager support of NTFS volume mount points, which is new in this version of SnapManager:

Drive letter limitations and individual database restoration

Windows supports up to 26 drive letters. Because SnapManager needs one LUN and therefore one available drive letter to perform backups, verifications, or restores, you can allocate a maximum of 25 drive letters. In addition, certain SnapManager operations require that additional drive letters be available:

Databases that need to be restored individually each require their own LUN and drive letter. If you have a large number of databases to be individually restored, you might run out of drive letters.
Performing a remote verification of more than one backup set requires a second LUN and therefore another available drive letter or mount point.

With previous releases of SnapManager for Exchange, you can avoid running out of available drive letters by determining which databases must be restored individually, and which can be combined on a LUN with one or two other databases (all of which are restored together). With this approach, you must still reserve at least one free drive letter for SnapManager.

With SnapManager 3.2 for Exchange, your configuration is not limited to the 26 drive letters supported by Windows. By using the NTFS volume mount point support that is part of SnapDrive, SnapManager can manage Exchange databases that are stored on mounted volumes as well as those stored on standard Windows volumes.

Mounted volume environments supported by SnapManager

The following table summarizes the environments in which SnapManager 3.2 for Exchange supports volumes mounted on Data ONTAP LUNs. Additional details regarding limitations and enforcement imposed by SnapManager are described in other sections of this document.

Microsoft Exchange	Windows host environment
	Windows 2000 Server		Windows Server 2003
	Stand-alone	Clustered 1	Stand-alone	Clustered
Exchange 2000	Yes		N/A²
Exchange 2003	Yes		Yes	Yes

¹ Windows 2000 Server does not support mounted volumes in a cluster.

² Microsoft Exchange 2000 is not supported on Windows Server 2003.

Mounted volume restrictions with SnapManager

In addition to the limitations inherent to the NTFS volume mount point feature of Windows (described in Understanding NTFS volume mount points), SnapManager imposes the following additional restrictions.

No Exchange database files on a mount point root

An NTFS volume that hosts mount points cannot also store Exchange database files. However, transaction log files can reside on such a volume.

The SnapManager Configuration Wizard does not allow you to place Exchange database files on an NTFS volume that has mount points.
SnapManager Backup does not allow you to back up a database on an NTFS volume that has mount points.
Note
If Exchange databases reside on a LUN, do not add mount points to that LUN, even after you finish a SnapManager backup operation. A subsequent LUN-level SnapManager restore operation would remove those volume mount points, disrupting access to the data on the mounted volumes referenced by these volume mount points.

Mounted volume naming conventions with SnapManager

A mounted volume is a volume that is mapped to a folder and referenced by a mount point that is created in an empty directory. The SnapManager user interface represents a mounted volume based on the path of a volume mount point that references that mounted volume, as follows:

DriveLetter:\MountPointName

where

DriveLetter represents the drive letter to which the mounted volume is assigned
MountPointName represents the mount point name assigned to the empty directory used to reference the mounted volume

Example:

F:\ My_Mount_Point

Using mounted volumes in SnapManager

The path-style representation of a mounted volume can appear in any part of the SnapManager user interface that refers to LUNs accessed by SnapManager:

Configuration Wizard screens that include a Disk List selection:
- Where to Move Databases
- Where to Move Transaction Logs
- Where to Move SMTP and MTA System File
- Where to Put the SnapInfo Directory
LUns that are referenced more than once: If the storage system is configured with multiple references to the same LUN, each such LUN reference is listed with a label that lists any other references to the same LUN. For example, suppose the drive letter H: and the mount point G:\DB\ reference the same LUN. In this case, the Disk List selection contains two entries for the one LUN:

LUN H:  <G:\DB\>

LUN G:\DB\  <H>

LUNs that have mounted volumes: If SnapManager accesses a LUN with an NTFS volume that is referenced by a mount point, that LUN is listed with a label that indicates this. For example, suppose the drive letter F: references a LUN that hosts a mount point. In this case, the Disk List selection lists that LUN as follows:

LUN F:  (MPRoot)

The Configuration Wizard does not allow you to store Exchange database files on LUNs that host NTFS volume mount points.
The location of the storage group components listed in the left navigation pane of the Backup and Verification Backup tab and the SnapManager Backup Wizard:
- SnapInfo directory
- EDB and STM paths
- Storage group log path
The location of the storage group components listed in the right display pane of the SnapManager Restore tab and the SnapManager Restore Wizard:
- SnapInfo directory
- EDB and STM paths
- Storage group log path
To specify which method is to be used to access database backup Snapshot copies during database integrity verification, use the Access LUN in Snapshot tab to assign either a drive letter or directory path to access the backup Snapshot copy as a mounted LUN. You can access this setting from the following locations within the SnapManager user interface:
- Configuration Wizard
- Options menu
- Backup Wizard
- Restore Wizard
For more information, see Selecting the Snapshot copy access method for database verification.