Tar and fbackup

[Prakash.D]

I want to know all the differences between tar and fbackup

Please give those different backups differences

[Bill Hassell]

tar is the classic Unix backup tool and is most useful in exchanging data between different Unix systems. It has no central index of files, but isjust a series of headers and files/directories. Because of it's age (decades old), it's format has been fixed and therefore has severe limitations. Standard tar is limited to files less than 2Gb and while a patch for HP-UX extends the limit to a mere 8Gb, such backups are unreadable on other platforms. The latest Gnu version of tar removes the file size limit but it's format is also incompatible with standard tar.

tar doe not have any error recovery in case of a bad spot on the tape, and does not handle multi-tape backups very well. And it is a single threaded, unbuffered process so it can't keep up with modern tape drives.

fbackup is a proprietary format just for HP-UX. As such, it is not useful for exchanging data between Unix or other systems. However, it has many features found only in commercial backup programs. It has a central index of all files at the front of each tape. It has the ability to handle multi-tape backups as well as manipulating a tape changer. It has error recovery to resync past bad spots on a tape, and is multi-threaded (technically, multi-process) so that data can be gathered very rapidly for today's ultra-speed tape drives.

The central index is a very important feature in that any file or directory can be restored in just a few minutes. fbackup verifies that a tape is not a previously recorded tape in the same multi-tape backup, and with frecover, can verify the backup tapes using special checksums. fbackup will handle any size files including terabytes.

So tar is useful in small backups primarily used for data interchange between non-HP-UX machines. It has simple options so it is useful in creating disk-to-disk tar archives, often called tarballs.

But fbackup is the tool of choice for full system backups, With a config file, it can keep the fastest tape drives running at full speed and has the reliability features to handle terabyte filesystems.

And of course, neither tar, cpio, dump or fbackup can restore a system to a blank disk. For that, you need Ignite/UX for a bootable image of the OS.