general tape questions

[Mark Henry_1]

Hi All,

Just after successfully attaching a Quantum DLT 4000 drive to an 11.0 workstation. After putting the 'stape' driver 'in', and rebooting, 4 device files were created - way too easy..

Is the stape driver used for all possible tape drives out there? What if there are other features that the drive supports apart from rewind and best compression?

What's the difference between the at&t and berkeley special file?

Once I write stuff to a tape, how do I..
a)know what's on there 6 months later? and
b)what space remains and how to jump to the end of the info I want to keep to continue writing to the tape..

Thx,

Mark

[James R. Ferguson]

Hi Mark;

Have a look at the man pages (section 1)for 'mt' [for manipulating tapes (rewinding, spacing forward, etc.)] and section 7 discussing tape device files and their nomenclature, etc:

# man 1 mt
# man 7 mt

Regards!

...JRF...

[Patrick Wallek]

JRF has given you good links for manipulating the tape device.

To answer your question about knowing what is on a tape 6 months down the road: You LABEL the tape! Put a label on the tape or in the tape case that you can read that says something like: "tar of /etc/data/oracle" or "full system fbackup" or something descriptive so you know how it was written (very important for restoring) and what should be there.

[Bill Hassell · Accepted solution]

>> Is the stape driver used for all possible tape drives out there? What if there are other features that the drive supports apart from rewind and best compression? <<

The device file is an option communicator between simple programs and the tape drive. Rewind, compression, immediate reporting, etc are all be setup by commecial quality
backup programs but simple tools like tar and cpio exercise little control over the tape features except via the device file options. You'll need to look over the HP-UX peripherals manuals at docs.hp.com.

>> What's the difference between the at&t and berkeley special file? <<

Read the man page for mt(7) (Unix speak, type the command: man 7 mt) Berkeley behavior is intuitive for positioning options, AT&T is, well, bizarre. The Berkeley device files are not created by default and you won't need to if you use a commercial backup program like Omniback.

>>Once I write stuff to a tape, how do I..<<

>>a)know what's on there 6 months later? and

As mentioned, paper labels are crucial if you are managing all your backup tapes by yourself. tar, cpio, pax, dump are all legacy programs that were never designed for the volume and size of data found on Unix systems today. Each of those tools can give you an index of the files that were saved BUT it will require reading the entire tape which can mean hours.

When your data exceeds one tape, there will be a lot of work needed to figure out a way to organize the backup tasks.

Commercial backup programs always place a table of contents at the beginning of the tape so an index can be read in a few seconds. And these programs handle multi-tape backups.

>> b)what space remains and how to jump to the end of the info I want to keep to continue writing to the tape.. <<

Wow, really bad idea. I've lost count of the number of calls I've gotten from a sysadmin that tried to save a few dollars by appending data to the end of tapes and lost everything when a small mistake was made. That's why fbackup does not allow appending to any tape and that commercial tools like Omniback can keep multiple backups across multiple tapes.

Backups are an insurance policy. The choice should should be made on the basis of the value data being protected. If it is valuable, then cheap insurance may fail when it is most needed.

[Ulrich Deiters]

"fbackup" writes a tape directory to your disk (and uses it when making incremental backups).

"tar" does not maintain tape inventories; it simply takes
whatever is offered and dumps it to the tape. But you can make your own tape inventory and save it by "tar" first,
before you save the other files.

[Randy Tarrier]

Mark,
In addition to all of the above, one q&d way to append files to a tape is to use the c & r options in tar:
cf creates a new archive, rf appends to an existing archive. I use this to stack Oracle archive log files to tape; however, I concur with the others where it comes to using a commercial program to backup critical data: "better safe than sorry".
Regards,
RLT