Image backup

From your local workstation, you can back up a logical volume as a single object (image backup) on your system.

The traditional static image backup prevents write access to the volume by other system applications during the operation.

You must be a root user to perform this task, and image backup does not apply to Mac OS X.

These volumes can be formatted NTFS or ReFS, or unformatted RAW volumes. If a volume is NTFS-formatted, only those blocks that are used by the file system or smaller than the imagegapsize parameter are backed up.

Normally you cannot restore an image backup of the system drive over itself since an exclusive lock of the system drive is not possible. However, in a Windows pre-installation environment (WinPE), an image restore of the system drive is possible. For information about restoring data in a WinPE environment, see technote 7005028.

You cannot restore an image backup to the volume on which the client is running. Consider installing the backup-archive client on the system drive.

Image backup does not guarantee consistency of system objects, such as the Active Directory. System objects can be spread out across multiple volumes, and should be backed up by using the backup systemstate command.

An image backup provides the following benefits:

• Backs up file systems that contain a large number of files faster than a full file system incremental backup.
• Improves the speed with which the client restores file systems that contain many small files.
• Conserves resources on the server during backups since only one entry is required for the image.
• Provides a point-in-time picture of your logical volume, which might be useful if your enterprise must recall that information.
• Restores a corrupted file system or raw logical volume. Data is restored to the same state it was when the last logical volume backup was performed.

The traditional static image backup prevents write access to the volume by other system applications during the operation. Use the dynamicimage option to back up the volume as is, without remounting it read-only. Corruption of the backup can occur if applications continue to write to the volume while the backup is running. Writing to a volume while an image backup is running can result in inconsistent data and data loss after a restore operation is run. The dynamicimage option overrides the copy serialization value in the management class to perform an image backup. After restoring an image backup taken with the dynamicimage option, always run the chkdsk utility.

The traditional offline image backup prevents write access to the volume by other system applications during the operation. When you backup an image by using snapshotproviderimage=none, always run the fsck utility after you restore the data.

To restore an image backup of a volume, the backup-archive client must be able to obtain an exclusive lock on the volume that is being restored.

Restriction: Do not use dynamic image backups for file systems, because the file system might provide inconsistent data even when there is no write activity. Also, dynamic image backup might result in a fuzzy image, which might not be valid or complete when restored.

If the backup-archive client fails to mount the file system after it restores an image, run fsck. However, running fsck can affect the integrity of large amounts of data. Do not use dynamic image backup for AIX® JFS2 file systems. The client does not allow dynamic image backup for AIX JFS2 file systems. If you specify dynamicimage=yes for a JFS2 file system, the client performs a snapshot-based image backup. If the snapshot cannot be created for some reason, the client instead performs a static image backup.

Attention: To prevent data loss, avoid using the dynamicimage option, and ensure that there is no write activity on the volume while the backup is in progress.

For AIX JFS2 file systems, the amount of data that is backed up to the Tivoli® Storage Manager server during static or snapshot image backup is reduced by backing up only those blocks used by the file system or smaller than the imagegapsize option. This method of backing up your data improves the performance of image backup. For more information, see Imagegapsize.

For AIX clients only: By default, the client performs an online snapshot image backup of JFS2 file systems, during which the volume is available to other system applications.

For Linux clients only: By default, the client performs a snapshot image backup of file systems that exist on a logical volume that is created by the Linux Logical Volume Manager. The volume is available to other system applications while the snapshot image backup is performed.

If online image support is configured, the client performs an online image backup, during which the volume is available to other system applications. The snapshot provider, as specified by the snapshotproviderimage option, maintains a consistent image of a volume during online image backup.

You can use the snapshotproviderimage option with the backup image command or the include.image option to specify whether to perform an offline or online image backup.

Attention: File systems that are managed by Tivoli Storage Manager for Space Management are not enabled for image backup.