disk image backup & normal maintenance backup

[Ahmad Munawwar]

Hi,

Would appreciate if anyone can help me to understand the different between disk image backup and normal maintenance backup system.

br,
Munawwar

[Karthik S S]

With disk image backup (like dd) you can not have incremental backups. What you can achieve is a clone of the source disk thus you will require that much of space. And the backup window for image backup will be very long. With normal backup tools like fbackup or other 3rd party applications (veritas netbackup, legato) .. you will have more control on the backup. You can take full, diffential, cumulative and incremental backups.

-Karthik S S

[Mark Grant]

A disk image backup is an "image" of the disk. i.e the fileystem/LVM data itself. IT will even backup the unused space. A restored disk image backup will have everything exactly the same as it was. Even down to position of the data on the disk. . You can not do a disk image restore to a smaller disk or even a larger disk (though it might work but there will be issues you'd rather not have to deal with).

A normal system backup will only backup the files on the disk. Therefore, when they are restored, they are recreated wherever you happen to restore them. These types of backup are what you generally will need.

[Ahmad Munawwar]

Hi,

I what condition normally we need to do the disk image backup?

br,
Munawwar

[Mark Grant]

You'll do a disk image backup usually in an emergency. If you want to copy exactly a failing disk or if you want to make another bootable disk with all the same data on it. Perhaps to put in another machine. You can use it on some systems to clone a machine though for HPUX ignite is better fo that!

[Karthik S S]

Also the biggest advantage of disk image backup is you can start using it almost instantly ..!!

-Karthik S S

[Leif Halvarsson_2]

Hi,
Some (most ?) backup programs , for ex. DataProtector/OmniBack can backup disks or logical volumes as filesystems or disk images (rawdisks). The advantage with filesystem backups is that it is possible to restore single files/folders and incremental backups is pollible. Disadvantage is slow backups if average filesize is small and disk system is slow. Image backups is for distsster recovery only, single file restore is not possible (at least not easy). Filesystem layout has no impact on performance, backup will run at full speed regardless of the structure and filesizes.