1. Administrator's Guide
  2. Media Management
  3. Overview

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.