Tape Media Groups

Tape Media Groups

Commvault^® software logically organizes all tapes into media groups. Each media group identifies all tapes associated with the group. Since all tapes are logically managed in the Commvault^® environment it is important to understand each media group and group management.

Using Scratch Groups

Scratch groups hold all new or recycled media. Multiple scratch groups can be used to define which tapes a job uses when it executes. When a job requires a spare tape, the tape is pulled from a defined scratch group. The storage policy copy data path is used to determine which scratch group the tape is selected from.

Key points and features for Scratch group:

• The terms: Scratch Pool, Scratch Group, Spare Media Group or Spare Media Pool are used interchangeably throughout Commvault documentation and the CommCell console
• All new and recycled tapes are placed in scratch groups
• Once a job is written to a tape it is moved out of the scratch group and into the assigned media group
• Multiple scratch groups can be created and assigned to storage policy copies. When a job for the policy copy runs, it automatically picks a tape from the assigned scratch group 

Managing Scratch Groups

By default, a default scratch group is created when the library is initially detected. From this point additional scratch groups can be created, and tapes can manually or automatically be assigned to the group. When jobs run, tapes are pulled from scratch groups and used for the job. Once data is written to the tape, it is moved out of the scratch group and into the assigned media pool.

When using multiple scratch groups, different storage policy copies define which scratch group tapes are pulled from. Also, tapes can be manually moved to other scratch groups or automatically assigned to different groups. Assigning tapes is based on barcode patterns or high watermark thresholds and scratch group priority. This allows different job types to be placed on specific media, which simplifies tape management outside the library.

Storage Policy using Different Scratch Groups

Storage Policy Copy Relationship to Scratch Groups

A storage policy copy data path includes the selection of a scratch group. By configuring multiple scratch groups and assigning them to storage policy copies, you can determine which tapes will be used to write certain jobs. Once data managed by the storage policy copy is written to the tape, the policy copy will own the tape until all jobs have aged. This means no other storage policy copies can write data to the tape.

Scratch Group Properties

Expand Media By Groups | Right-click the scratch group | Properties

High and low watermarks are assigned to each scratch group in a tape library. Low watermarks are used to alert administrators when the library is running out of spare tapes. The high watermark is used to limit the number of tapes placed in a scratch group.

Key points for configuring high and low watermarks:

• Low watermarks – Reports events in the Event Viewer when scratch tapes fall below the defined number. Alerts can also be configured to alert administrators when low watermarks are reached.

• High watermarks – Limits the number of tapes that will be assigned to a scratch group. This is useful when multiple scratch groups and custom barcode pattern definitions are not being used. Scratch groups can be assigned high, medium and low priorities. When tapes are discovered or recycled, they are placed in the high priority scratch group until it reaches the upper watermark. The medium group is filled next followed by the low priority group. If there are still additional tapes available, they are placed in the Default Scratch group designated in the General tab of the library properties.

Tip: Using multiple scratch groups to ensure available media for backup operations
You are managing a CommCell^® environment and running backup jobs directly to tape each night. During the day, you run auxiliary copy jobs to tape to be sent off site. You are concerned that auxiliary copy jobs may use too many tapes and there will not be enough media for backup operations.

Solution: Create an additional scratch group and name it Auxiliary Copies. Set the priority to Medium. Configure a High Watermark in the Default Scratch group to be a greater number than the number of tapes required to perform nightly backups. Set the Default Scratch group priority to high.

In the secondary copy of each storage policy, use the Scratch Pool drop-down box to assign the Auxiliary Copies scratch pool to the copy.

Cleaning Media Group

Expand the library | Media By Groups | Cleaning Media

The Cleaning Media group manages all cleaning tapes for a library. Tape drives are cleaned based on drive counter usage tracked by Commvault^® software and/or sense codes reported from the library. Drive cleaning settings are configured in the library properties under the Drive tab.

Best practice guidelines are to configure drive cleaning based on the library manufacturer's recommendations.

Key points for the Cleaning Media Group:

• Commvault software should automatically detect and move cleaning tapes to the cleaning media group when the tapes are discovered.
• If cleaning tapes are incorrectly identified and moved to a scratch pool, you can manually move the tapes or use custom barcode definitions to associate cleaning tapes with the cleaning media pool.
• Low watermarks can be defined to trigger events and optional alerts when the number of spare cleaning media reaches the low threshold. 

Retired Media Group

Expand the library | Media By Groups | Retired Media

The Retired Media group is a holding area for all tapes that have exceeded tape error thresholds or are manually marked bad. Tapes in the Retired Media group will remain in the group until they are manually marked good or deleted. Any tapes in the Retired Media group will NOT be written to. If a tape is in the Assigned Media group and is marked bad, it will NOT be moved to the Retired Media group until all jobs have aged from the tape.

Key points for the Retired Media group:

• Only tapes that are not currently retaining job data are placed in the retired media group. If a tape is marked bad but is currently retaining data, it will still appear in the Assigned Media group. Once all jobs have aged from the tape it is moved to the Retired Media group.
• Tape counters are tracked for the life of a tape from initial discovery to deletion.
• By default, manufacturer-recommended thresholds are used for all tapes. These settings can be modified in the Control Panel | Hardware Maintenance applet | Media Retirement tab. It is NOT recommended to increase the threshold values.
• For as long as a tape is in the Retired Media group it will NOT be written to.
• Tapes can be moved out of the Retired Media group using the following methods:
  • Delete – Deletes the existence of the tape from the CommServe^® server database. The tape can then be rediscovered and reused. The tape is treated as a brand-new tape and all counters are reset. If there are any existing aged jobs on the tape they will not be recoverable.
  • Mark Media Good – Is recommended if the tape has existing jobs that have aged but may still need to be retained. If this is the case after marking the tape good, move it to the Overwrite Protect Media group.

Tapes should be left in the Retired Media group until they are physically disposed of. This prevents a bad tape from accidentally being discovered and reused. If a bad tape is disposed of and is replaced with a new tape with the same barcode, delete the tape from the Retired Media group before putting the new tape in the library.

Tip: Tapes incorrectly marked bad
Sometimes tapes can be incorrectly marked bad due to drive problems that result in tape errors. If there is a sudden increase in bad tapes this may be an indication of drive problems. However, do NOT discount the possibility that the tapes are bad. There have been situations where bulk orders of brand new tapes are legitimately bad. If you do not know what manufacturing, delivery, or storage methods are being used; then it is critical to act on the side of caution.

Foreign Media Group

Expand the library | Media By Groups | Foreign Media

The Foreign Media group manages all media from different CommCell^® environments or tapes from a different backup vendor.

Key points for the Foreign Media Group:

• Tapes from one CommCell^® environment cannot be directly restored into another. When a tape is loaded and the OML (On Media Label) header is read, if the CommCell ID is different than the CommCell^® environment reading the tape, the tape is moved to the Foreign Media group.
• Commvault software will not write to tapes when the OML header is not recognized as a Commvault header and the tape is moved to the Foreign Media group.

Overwrite Protect Media Group

Expand the library | Media By Groups | Overwrite Protect Media

The Overwrite Protect Media group logically locks down a tape, so it will NOT be written to or recycled. Tapes must be manually moved to the Overwrite Protect Media group and remain there indefinitely until they are moved out of the group.

Key points for Overwrite Protect Media group:

• By default, an Overwrite Protect Media group is automatically created. Additional overwrite protect media groups can be added.
• Tapes are moved to the Overwrite Protect Media group using the following methods:
  • For active tapes in the Assigned Media group – Right-click on the tape and select Prevent Reuse. The tape appears in the Assigned Media and the Overwrite Protect Media groups.
  • For tapes in scratch groups – Right-click on the tape and select Move. For Media Group Type select Overwrite Protect Media group and then select the overwrite group.

Tip: Other methods to prevent tapes from being overwritten
Moving a tape to the Overwrite Protect Media group is just one-way Commvault^® software can prevent data from being overwritten. Data can also be locked down at the job level.

Consider a job that spanned multiple tapes. Manually moving tapes to the Overwrite Protect Media group requires you to know every tape the job was written to. The job and all tapes can also be locked down through the storage policy copy. In the job history of the policy copy, right-click on the job and select Retain Job. You are then prompted to select a date to hold the job, or infinitely retain the job. 

Catalog Media Group

Expand the library | Media By Groups | Catalog Media

The Catalog Media group is used to hold all tapes that are actively being cataloged or are marked for catalog. A catalog operation is used to catalog job metadata from a tape and enter the metadata back into the CommServe^® server database. You can perform this operation if the CommServe server database had to be restored to a point-in-time prior to the jobs on a tape finishing. This situation can arise in cases of disaster, database corruption, or if the CommServe server metadata backups are not properly managed.

A tape can be individually picked for catalog or multiple tapes can be picked and marked for catalog. When tapes are picked for catalog they are moved to the Catalog Media group.

Assigned Media Group

Expand the library | Media By Groups | Assigned Media

All tapes that are actively retaining data are located in the Assigned Media group. Within a library, there is only one assigned media group. Tapes remain in the group until ALL jobs on the tape have exceeded retention and are marked as aged. During the data aging operation, the tape is then recycled back into a scratch pool.

Key points regarding tapes in the Assigned Media group:

• Tapes in the Assigned Media group cannot be deleted. Delete is considered a non-destructive operation.
• Delete Contents can be performed on a tape which is considered a destructive operation. To delete the contents of multiple tapes, use the Shift or Ctrl keys to select multiple media. Note that this recycles the tape and the jobs are marked aged.

Assigned Media Relationship to Storage Policy Copies

When a spare tape is picked for a backup job, the tape becomes associated with the storage policy copy that is managing the job. This is important to understand because once the tape is associated with the policy copy, no jobs from other policy copies can be written to the tape. This is done intentionally to avoid mixed retention on media. Since each storage policy copy can have different retention configured, it is important to separate jobs based on policy copy ownership.

Since tapes are associated with storage policy copies it is important to properly configure and manage storage policies.

Tip: Consequences of having too many storage policies using tape media
Your environment has 25 storage policies. This results in at least 25 storage policy primary copies. If all primary copies are defining tape library data paths, then at least 25 tapes must be in the library to accommodate all potential jobs. If the storage policies also have secondary copies using a tape data path, then additional tapes must also be present to meet the media needs of the secondary copies.

In some cases, backup configurations such as Start New Media and Mark Media Full can complicate things more. It is important to understand your environment's needs and how Commvault software manages media.

Use global secondary copies to consolidate data from multiple storage policy secondary copies to the same tape sets.