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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.
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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.
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For AIX JFS2 file
systems, the amount of data that is backed up to the IBM
Spectrum Protect 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.
For Linux clients: Image
backup of DASD devices with raw-track access mode on Linux on
z Systems® is not supported.
The image backup operation is not supported on any
partition that resides on a multipath device.
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.
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