Disk Libraries - Best Practices

Disk Library

Once you configure a disk library, we recommend that you perform or schedule frequent Auxiliary Copy operations to a secondary storage such as tape media. This will ensure that you have a copy of the backup data in case of disk failure.

Defining Mount Paths

You can define one or more mount paths to local or remote computers for Windows and UNIX file systems. You cannot define mount paths to a disc drive, for example, CD-ROM drive, or a locally mapped network drive.

If the mount path directory does not exist, it is automatically created when you add the mount path.

If you have defined multiple mount paths for a disk library, the system determines the specific path to which data secured by a data protection operation is written.

Using Dedicated Partitions

Use dedicated partitions for your disk mount paths to ensure that the MediaAgent always accesses the mount paths allocated to disk libraries:

We recommend the following practices for creating mount paths:

  • Do not create a mount path on the same partition where the MediaAgent software is installed.
  • Do not create a mount path under an already existing CV_MAGNETIC folder.

Storage Space for Mount Path

Make sure that each mount path contains at least 2 GB of free space when it is created, and that the total storage space in the disk library is sufficient to hold the maximum amount of data that will be stored in the library at any time.

Using a UNC Path as a Mount Path

If you want to use a path to a remote Windows computer as a mount path, the mount path must be added using the UNC (Universal Naming Convention) format as follows:

\\<computer name>\<shared directory name>\<optional path>

Note: Do not use name 'Commvault' as the <optional path>. For example, \\<computer name>\<shared directory name>\commvault.

Consider the following while adding a UNC path as the mount path:

  • If the mount path is in a different domain from the MediaAgent from which it is accessed, make sure that trust relationships are setup between the two domains.
  • Before adding the UNC path, verify and ensure that the UNC path is accessible from another computer using the domain account that will be used to access the mount path. (If the mount path and the MediaAgent are on different domains, make sure to perform this test across domains.)
  • The user account used to access the mount path must have read / write permissions to the software install folder on the MediaAgent accessing the mount path. The MediaAgent uses these folders to add log entries for jobs associated with the mount path.
  • The mount path for a disk library in a clustered environment should be a UNC path or the shared disk on a cluster.

Mount Path to a Remote UNIX Computer

An NFS mounted file system can be used as a mount path to a remote UNIX computer. The system considers an NFS mounted file system local to the computer where it is mounted.

Accessing Mount Paths

The software does not permit the creation of two mount paths that access the same directory. This is true even if one mount path accesses the directory locally while another mount path accesses it remotely.

Creating Multiple Mount Paths in the Same Volume

For UNC mount paths, avoid adding mount paths that utilize the same disk as separate volumes as this can lead to incorrect storage calculations.

For example, \\Computer_name\share1 and \\Computer_name2\share2 are UNC mount paths that are using the same volume and both the mount paths will report having X amount as the total capacity leading to an incorrect 2X calculation.  For example if the volume size is 4 TB, both the mount paths will report 4 TB as total capacity, leading to an incorrect calculation of 8 TB as total capacity.

Mount Path Is Marked as Offline

If a disk volume in Windows platform is found to be dirty, the volume is marked offline. Any attempts to access the volume will result in error. Clean up the volume and manually bring it back online.

If a mount path directory is deleted or renamed (that is, through the operating system), it is not recreated the next time a data protection operation attempts to accesses the mount path. The mount path becomes inaccessible for the job and hence the mount path is marked as offline. Attempts to back up to that mount path will generate error messages.

Maximum Number of Writers

The maximum number of writers for a disk library is used to determine the maximum number of concurrent write operations. Hence this value is linked to the maximum number of data streams that can be established for a storage policy accessing the disk library.

The values for writers can be modified from the Disk Library Properties and Mount Path Properties dialog box available in the CommCell Console. The values for the maximum number of data streams can be modified from the Storage Policy Properties dialog box also available in the CommCell Console.

Storage Policy Data Streams

Storage Policy data streams are logical channels that connect client data to the media where the data that is secured by data protection operations is stored. Multiple data streams can be used to run an operation simultaneously to improve the rate at which data can be written to the media.

The practical limits for establishing data streams in a storage policy that accesses a disk library is determined by the minimum value established in either the disk library or the sum of mount paths in the disk library.

Enabling Power Saving Mode

You can enable the disk spin-down feature, which is a power saver mode depending on your particular setup. You may consult the hardware vendor to verify if the disk spin-down feature is enabled or disabled on your disk array if you are experiencing data access or throughput delay.

GFS2 Support

GFS2 is not supported for use as a disk library target due to locking / performance issues that do not scale.

Excluding Mount Paths from Antivirus software

Exclude the CV_MAGNETIC folder (or the entire disk where CV_MAGNETIC folder resides) from all software and hardware antivirus security software solutions, to prevent locking issues with the mount path. When your antivirus security software is in the process of scanning the CV_MAGNETIC folder on library mount paths, Commvault software cannot access the folder.

Isilon Optimizations

Set the following parameters to optimize the read operations on Disk libraries configured on Isilon servers:

  • 16 GB as the chunk size

    Chuck size for the Disk library can be set in the MediaAgent Properties in which the library is configured. For more information on setting the chunk size, see Controlling the Chunk Size in the MediaAgent.

  • 2 MB as the data path block size

    Data Path block size can be set from the Data Path Properties dialog box available from the Data Paths tab of the Copy Properties dialog box, for the specific data path.

Last modified: 12/21/2017 3:07:39 PM