remote backup spanning multiple tapes using tar

[Vinod Kashyap P]

Hi,

I am using "rsh" to execute tar command on the HP-UX machine to which the tape drive is connected.Once the end of tape is reached, i get the following message:
"Can't open /dev/tty to prompt for more media".
and the tar command dies after taking incomplete backup.The tar command is unable to prompt on the terminal.Please suggest me how to comeover this problem, so that i can take the complete backup spanning multiple tapes using the "tar" command itself.

Regards
Vinod

[Corthouts Carlo]

Hi,

Maybe consider using fbackup.

[Bill Hassell]

I would be very concerned about making a complete backup using tar over the network, The are concerns about with reliability and as you've seen, there is no way to interact with a remote tape device. tar is far too simplistic to understand network backups and multiple tapes.

Also note that tar (and cpio and pax and ftio) are not capable of storing large files (files greater than 2gb). This is by industry standard. However, as mentioned, fbackup is a much better choice as it is network-aware and can be scripted to handle end-of-tape conditions including loading new tapes using autoloader commands.

Since you mentioned a full backup, be sure you setup an Ignite/UX server so you can backup your vg00 volume over the network and restore it to a new root disk, should the current disk go bad. Neither tar or fbackup can perform this specialized task.

[Steve Steel]

Hi

http://searchhp.techtarget.com/tip/1,289483,sid6_gci512097,00.html


This statement via techtarget says it all

MALLETT: HP-UX ANSWER MAN

Using tar? Don't get "tar"'d and feathered.

Fred Mallet
08 Jan 2001, Rating 4.29 (out of 5)



Most system administrators have heard the warnings against using the tar command for tape backup. The cliche statement is usually "tar does not handle errors well". This is a very correct answer, though it is not very descriptive. Lets dig a little deeper.

The cliche statement refers to the fact that most tar versions, upon encountering an error reading from a tape, will abort. This means that an error on a tape being read will render the remaining data on the tape inaccessible. This could mean lots of good data on the tape that cannot be read, since you cannot get past the error. .

Another similar issue with tar is that it does not checksum the data itself, only the header information. This means that tar could restore corrupt data without informing you. .

A final issue is that the format of tar headers only allows 100 characters in a pathname. This is way too short for many application trees, and possibly for data directories. You can create single filenames up to 255 characters, so theoretically you could exceed tar's limit with a single file. Of course, only people below a certain threshold of intelligence would do that. .

What all this boils down to is that you should probably never put anything important onto a tape with tar. But it is almost self-evident that anything you want to put out on tape is important. The obvious solution is to use tar only for creating 'tarballs' (tar archive files) for the purpose of moving data around the network, or from disk to disk. .

Better commands for writing to tape are the supplied backup programs (fbackup), cpio, dump, or a purchased backup program. .

Another solution is to grab the GNU version from www.gnu.org, which solves some of these issues, but creates GNU-tar format tapes. .

The POSIX movement created the pax command, which is a replacement for tar, but I have heard conflicting claims as to it's tape error handling. .

USE FBACKUP

Steve Steel

[steven Burgess_2]

Hi

Command is

#:\> fbackup -0v -i / -f :/dev/rmt/????


Steve