Administrator's Guide

Storage Pools

ADSM has two types of storage pools that serve different purposes: primary storage pools and copy storage pools.

Primary storage pool

When a client node backs up, archives, or migrates data, the data is stored in a primary storage pool.

When a user tries to restore, retrieve, recall, or export file data, the requested file is obtained from a primary storage pool if possible. Primary storage pool volumes are always located onsite.

A primary storage pool can use random access storage (DISK device class) or sequential access storage (for example, tape or FILE device classes).

ADSM has three default, random access, primary storage pools:

ARCHIVEPOOL

Contains files archived from client nodes

BACKUPPOOL

Contains files backed up from client nodes

SPACEMGPOOL

Contains files migrated from client nodes via the client hierarchical storage management (HSM) function (space-managed files)

ADSM does not require a separate storage pool for space-managed files, but a separate storage pool is recommended. Clients are likely to require fast access to their space-managed files, and therefore you may want to have those files stored in a separate storage pool that uses your fastest disk storage.

Copy storage pool

When an administrator backs up a primary storage pool, the data is stored in a copy storage pool. See "Backing Up Storage Pools" for details.

The copy storage pool provides a means of recovering from disasters or media failures. For example, when a client attempts to retrieve a file and the server detects an error in the file copy in the primary storage pool, the server marks the file as damaged. At the next attempt to access the file, the server obtains the file from a copy storage pool.

ADSM attempts to access the file from a copy storage pool if the primary copy of the file cannot be obtained for one of the following reasons:

• The primary file copy has been previously marked damaged (for information about damaged files, see "Correcting Damaged Files")

• The primary file is stored on a volume that is UNAVAILABLE or DESTROYED

• The primary file is stored on an offline volume

• The primary file is located in a storage pool that is UNAVAILABLE, and the operation is for restore, retrieve, or recall of files to a user, or export of file data

For details, see "Restoring Storage Pools", "Using Copy Storage Pools to Improve Data Availability", "Recovering a Lost or Damaged Storage Pool Volume", and "Maintaining the Integrity of Files".

A copy storage pool can use only sequential access storage (for example, a tape or FILE device class).

Copy storage pool volumes can be moved offsite and still be tracked by ADSM. Moving copy storage pool volumes offsite provides a means of recovering from an onsite disaster.

An Example of Server Storage

Figure 15 shows one way to set up ADSM server storage. In this example, the storage defined for the server includes:

• The three default disk storage pools, all primary storage pools
• One primary storage pool consisting of tape cartridges
• One copy storage pool consisting of tape cartridges

For each of the three disk storage pools, the tape primary storage pool is next in the hierarchy. For more information about setting up a storage hierarchy, see "The Storage Pool Hierarchy".

All four of the primary storage pools can be backed up to the one copy storage pool. For more information on backing up primary storage pools, see "Backing Up Storage Pools".

Figure 15. Example of Server Storage

Comparing Primary and Copy Storage Pools

Table 15 compares the characteristics of primary and copy storage pools.

Table 15. Comparing Primary and Copy Storage Pools

Characteristic	Primary storage pool	Copy storage pool
Destination for backed-up or archived files (specified in backup or archive copy groups)	Yes	No
Destination for space-managed files (specified in the management class)	Yes	No
Offsite access mode for volumes	No	Yes, except for volumes with device type SERVER
Destroyed access mode for volumes	Yes	No
Random access storage volumes	Yes	No
Sequential access storage volumes	Yes	Yes
Contents	Client files (backup versions, archived files, space-managed files)	Copies of files that are stored in primary storage pools
Moving data allowed	Within the same primary storage pool, or to any primary storage pool	Within the same pool only. If volumes are offsite, data is copied from the original files in primary storage pools.
Collocation	Yes (sequential access storage pools only)	Yes
Reclamation	Yes (sequential access storage pools only)	Yes Virtual volumes (volumes with device type SERVER) and offsite volumes are handled differently. For details, see "Reclamation of Volumes with the Device Type of SERVER" and "Reclamation of Offsite Volumes".
File deletion	Files are deleted: During inventory expiration processing, if the files have expired When a file space is deleted When a volume is deleted with the option to discard the data When a primary storage pool volume is audited with the FIX=YES option, if the files on the volume are damaged and no other copies of the file exist	Files are deleted: Whenever the primary copy of the file is deleted from the primary storage pool (because of expiration, file space deletion, or volume deletion) When a volume is deleted with the option to discard the data When a copy storage pool volume is audited with the FIX=YES option, if the files on the volume are damaged