How ISM Uses Volume Pools

ISM uses pools of volumes to sort and organize your storage space and logical-log backups. A volume pool is a collection of storage volumes. Any tape and optical disk storage volume can belong to the same volume pool. When you initiate an ON–Bar backup, ISM directs the data to a specific volume pool rather than to a specific volume. If ISM detects that a volume from the correct pool is mounted on a storage device, ISM writes data to that volume, regardless of media type.

Every storage volume belongs to a specific pool of volumes. ISM uses two types of volume pools, Backup and Backup Clone. Data cannot be mixed between pools of differing type. This situation enables ISM to keep original and cloned data separate. ISM ships with the following pools for use in backup and cloning operations:

• ISMData pool. Storage volumes in this pool accept backups of your storage spaces.
• ISMLogs pool. Storage volumes in this pool accept backups of your logical-log files.
• ISMDiskData pool. Storage volumes in this pool accept backups of your storage spaces when you use a file-type storage device. Volumes in this pool are of media type file and cannot be mixed with volumes of other media type.
• ISMDiskLogs pool. Storage volumes in this pool accept backups of your logical-log files when you use a file-type storage device. Volumes in this pool are of media type file and cannot be mixed with volumes of other media type.
• ISMData Clone pool. Storage volumes in this pool accept clones of your storage-space backups.
• ISMLogs Clone pool. Storage volumes in this pool accept clones of your logical-log backups.

We recommend that you use the ISMData and ISMData Clone pools for storage spaces and the ISMLogs and ISMLogs Clone pools for logical logs. If you use file-type storage devices, use the ISMDiskData and ISMDiskLogs pools for the file-type volumes.

ISM also ships with several other preconfigured pools that are included for forward compatibility, as follows:

• Default
• Default Clone
• Full
• NonFull
• Offsite

Writing to Volumes of Different Media Types

Figure 7 illustrates how ISM writes data to volumes of different media type that both belong to the same pool.

Figure 7. Volume Pools That Contain Varying Media Types

You cannot include storage volumes for file-type devices in a volume pool that includes other types of volumes. ISM does not allow volumes of other types to be recycled or added to a pool of file-type volumes. If you use file-type devices, it is recommended that you use the ISMDiskData and ISMDiskLogs pools with file-type volumes. You can then clone the data from your ISMDiskData backups to tape volumes.

For details on the recommended storage-device configuration when you use file-type devices, see Using Filesystems as Storage Devices. For details on the cloning feature, see Cloning Storage Volumes. For information on how to choose which volume pool is used for backups, see the Using ISM Environment Variables.

Using Volume Pools and Volume Labels

The volume label determines the volume pool to which a storage volume belongs. ISM maintains a record of each volume in the ISM catalog. ISM uses the ISM catalog to identify volumes that it needs for backing up and recovering data.

Each volume pool has a matching label format associated with it. ISM automatically uses the label format associated with the pool that you choose. These label formats provide a method for consistently naming and labeling volumes.

ISM automatically labels a volume with the next sequential label available for that volume pool. The label names are recorded internally on the media, creating an electronic volume label.

The preconfigured ISMData and ISMLogs label formats automatically use the ISM server hostname, the appropriate pool name, and a numbering scheme that labels the volumes from 0001 to 9999, as the following table shows.

Label

Use

nova.ISMData.0024

This volume is from the ISMData pool and contains storage spaces from a host named nova.

nova.ISMLogs.0012

This volume is from the ISMLogs pool and contains logical logs from a host named nova.

The following table lists the pools that you should use for your storage spaces and logical logs and the format of the resulting volume label.

Use the ism_op -label device command to label a volume. After a volume is labeled and mounted, it is available for backups. You can label several volumes at once without dismissing the dialog box, if you prefer. For details, see ism_op.

Using Expiration Dates for Volume Labels

Whenever you label or relabel a storage volume, ISM automatically assigns a two-year expiration date to the volume. This expiration date applies to the physical media and is different from the retention period that you assign to your data. When a volume reaches its two-year expiration date, ISM marks the Backup status for the volume as Disabled. To minimize the failure rate of older media, ISM cannot write new data to the volume. The ISM server still tracks the data on the volume and applies the retention period to the save sets on the volume. Until the volume is relabeled, you can recover the data. When you relabel a storage volume, it receives a new two-year expiration date.