N Media Management

This chapter discusses how to manage the same type of media recorded in different densities and how to separate cartridges written in the old density from cartridges written in the new density.

Overview

In this overview, you gain an understanding of:

Restrictions and the possible problems you may encounter
Examples of tape drives that record on the same media in different densities
Recommended solutions

Restrictions

Often, new tape drives are introduced that use existing tape media, but record at a higher density. These new drives can often read tapes recorded in the old density, but they cannot write in the old density. The older tape drives can neither read nor write in the higher density.

Because of these restrictions, you may encounter the following problems:

When a tape written in the new density is mounted on an older drive, the older drive cannot read the tape.
When storage management applications try to fill-up partially used tapes by appending additional files at a later time, it will fail if the tape was written using a different density than one to which a new tape drive can read but cannot write.

If you have a mix of both older and newer tape drives in your libraries, you must manage your tape cartridges that are of the same media type.

Examples

The following examples show tape drives that record on the same media, in different densities:

T10000 Media used by T10000A and T10000B Tape Drives

The T10000B tape drive uses the same media as the T10000A, but writes data at double the T10000A's density. The T10000B can read T10000A media and can reclaim (write from beginning of tape) it for writing T10000B density data, but it cannot append data to a previously written T10000A.

The T10000A drive can reclaim a T10000B cartridge for writing T10000A density data, but can neither read from, nor append data to a T10000B cartridge.
9840 Media used by T9840C and T9840D Tape Drives

Manage 9840 media when a combination of T9840A, T9840B, T9840C, and/or T9840D drives are present, because:
- T9840C
  
  The T9840C uses the same media as the T9840A and T9840B, but records at double the density.
- T9840D
  
  The T9840D writes at almost double the T9840C drives density.
  
  Manage 9840 media when a combination of T9840A, T9840B, T9840C, and/or T9840D drives are present.

Solution

ACSLS has tools you can use to manage common media on which two or more types of drives can write, but are in incompatible recording densities. The client application must use these tools to manage the read/append data incompatibilities.

Manage drives that record on common media in different densities within an ACS by either:

Replacing all of the older drives in an ACS with the new drives at the same time.

This is the simplest and safest strategy. Using this strategy, you avoid the problems caused by managing a combination of drives using different densities. If you are unable accomplish this, you can gradually replace the older drives with the new drives, as discussed in the second bullet.

Note:
Do not append files to any tapes written in the old recording density after replacing the old drives with the new drives. With Veritas NetBackup, this is done by suspending the tapes.
Gradually replacing the older drives with the new drives.

This requires you to manage the common media recorded in different densities. You can do this by:
- Using the recording format information returned when the cartridge is dismounted in SL8500 and SL3000 libraries to manage media. This is discussed in the next section.
- Creating separate ACSLS pools for each format.
- Using the facilities of a backup application (for example, Veritas NetBackup, Legato NetWorker, IBM Tivoli, or CA BrightStor) to manage media pools.

Managing Common Media with Recording Densities Reported by ACSLS

When a cartridge is dismounted from a modern tape drive in a modern library, the recording format of the cartridge is reported to ACSLS. ACSLS saves the recording format in its database. You can use the display volume command to display this information.

Recording format is reported by:

Libraries:
- SL3000
- SL8500 (with 4.10 or later firmware)
Tape Drives:
- All T10000 tape drives (with 1.38 or later firmware)
- T9840C and T9840D

The example below describes how to manage T10000 media recorded in both T10000C and T10000D formats.

Note:

The discussion below uses the following syntax conventions for commands and utilities:

Commands and Utilities entered as is are in bold.
Variables (you must enter the exact value) are in italics.

Procedure

After the T10000D drives are installed, use the recording format information to mount cartridges on compatible tape drives. Again, cartridges written at T10000C density can be read by either T10000C drives or T10000D drives, but only T10000C drives can append data written in a T10000C format. Only T10000D drives can read or append to cartridges written in a T10000D format.

No special processing is necessary when mounting scratch cartridges. When you write the cartridge from beginning-of-tape, the previous recording format does not matter.

To select a drive to read or append to a cartridge with data already recorded on it, follow this procedure. The following commands identify drives that can read and write a cartridges recording format.

Mounting Non-scratch Cartridges

Display the recording format of the cartridge.

display volume vol_id -f recording_format_family recording_format_model

The recording format for this volume is displayed.
Use the following query command to identify a compatible drive:

query mount vol_id

Drives compatible with a cartridge are displayed.
- Select the correct drive type before mounting the cartridge.
  
  This query command returns both T10000C and T10000D drives (because both drive types are compatible with T2 media).
- Use the drive type to separate T10000Cs from T10000Ds.
  
  Selecting the first compatible drive in the list minimizes pass-thru and improves library performance.
Mount the cartridge on a drive compatible with the recording format with the following command:

mount vol_id drive_id

Migrating to the New Recording Format

When all the data on the cartridge has expired, you can re-write the cartridge from beginning-of-tape, in a new recording format.

For more information on expired cartridges, refer to "Populating the LSM".
After all T10000C drives are converted to, or replaced by T10000D drives, all T2 media can be used by T10000D drives if data is not appended to cartridges written in T10000C format.

Managing Common Media Recorded in Different Densities with ACSLS Pools

The following procedure applies to all cases where different tape drives record on a common media, in different densities. Use the following table to apply the procedure to your specific case:

Old Format Drive(s)	New Format Drive(s)
T10000C	T10000D
T9840C	T9840D
LTO 7	LTO 8

Procedure

Identify all LTO data (non-scratch) cartridges in the ACS, and assign them to a LTO 7 pool. Do this before installing LTO 8 drives in an ACS that has LTO 7 drives.

Now you can assign LTO scratch cartridges to either the LTO 7 or LTO 8 pool.
1. Define LTO 7 and LTO 8 media pools using the following command:
  
  define pool pool_id
2. Report all LTO 7 media.
  
  You can do this by using either the display volume command (option 1) or a custom volrpt (option 2), as shown below:
  
  Results write a file.
  - Option 1
    
    Use the display volume command to write the results to a file.
    
    display volume * -media LTO-6.4T > filename
    
    where:
    
    All LTO 7 tape cartridges (media LTO-6.4T) are reported.
    
    filename is the filename to which the output is written. The ACS ID in which the cartridge is located is also listed.
    
    Read the output, selecting cartridges from specific ACS(s), if desired.
    
    If you want cartridges from one ACS, use the -home operand to only select cartridges from this ACS.
    
    display volume * -home acs_id.*,*,*,* -media LTO-6.4T> filename
  - Option 2
    
    Use the custom volrpt for all volumes in the ACS. The results write a file:
    
    volrpt -d -f custom_volrpt_file -a acs_id > filename
    
    where:
    
    custom_volrpt_file is the filename specifying the fields reported in a custom volrpt. The following fields are reported:
```
VOLUME_ID      6   2
MEDIA_TYPE     7   2
VOLUME_TYPE    4   2 
```
    acs_id is the ID of the ACS that you are managing.
    
    filename is the filename to which the output is written.
  Read the output, selecting only the volumes with a media type of LTO-6.4T.
3. Assign the selected volumes to the appropriate pools.
  
  Assign all non-scratch (VOLUME_TYPE = D) cartridges to the LTO 7 pool using the following command:
```
set scratch off pool_id vol_id
```
  Assign the scratch cartridges (VOLUME_TYPE = S) to either the LTO 7 or LTO 8 pools using the following command:
```
set scratch pool_id vol_id
```
After the LTO 8 drives are installed, use the pools to mount cartridges on compatible tape drives.

Again, cartridges written at LTO 7 recording density can be read by either LTO 7 drives or LTO 8 drives.

The following commands can be used to identify, select and mount cartridges from the pool appropriate for an LTO 7 or LTO 8 drive. Use the pools to ensure you are mounting cartridges on the correct drive.

Note:
If you want to mount a scratch cartridge on the correct drive type, follow procedure A. If you want to mount a non-scratch cartridge with data already recorded on it, follow procedure B.

Procedure A - Mounting Scratch Cartridges
1. Query drive(s) to identify drive types.
```
query drive drive_id | all  
```
2. Identify the correct pool (media type) for the cartridges to be mounted on the desired drive.
3. Mount scratch cartridges to a drive from the specified pool.
```
mount * drive_id pool_id
```
Procedure B - Mounting Non-scratch Cartridges
1. Display the status of drives compatible with a cartridge.
```
display volume vol_id -f pool 
```
  The pool for this volume is displayed.
2. Identify a compatible drive using the query command.
```
query mount vol_id
```
  Drives compatible with a cartridge are displayed.
  
  Select the correct drive type before mounting the cartridge. This query command returns both LTO 7 and LTO 8 drives (because both drive types are compatible with LTO-6.4T media).
  
  Use drive type to separate T9940As from T9940Bs.
3. Mount the cartridge on the selected drive.
```
mount vol_id drive_id
```
When all of the data on the cartridge has expired, you can migrate the scratch cartridges to the pool for the new recording density. Because LTO 7 and LTO 8 drives can re-initialize cartridges in their density, scratch cartridges can be reassigned to a different pool.
```
set scratch pool_id vol_id
```
After all LTO 7 drives are converted to, or are replaced by LTO 8 drives, all LTO-6.4T media can be used by LTO 8 drives.