UNIX Checking Tape Space

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Operating Systems Solaris UNIX Checking Tape Space
# 1  
Old 11-20-2013
UNIX Checking Tape Space


My name is Alex and I am new to the UNIX environment.

One of the things that I do on a daily basis is I perform backups to tape on a Sun Ultra 25. I use DAT72 tape.

The tape that is currently in the tape drive has about five database backups within it already. I was just hoping to find out if there is anyway possible that I can verify how much space is available. Also, how can I find out how big my database file is?

Thanks in advance for those who help me out with this issue.

# 2  
Old 11-20-2013
Tape doesn't have a filesystem the way a disk does, everything is contiguous. This means it can't have a filesystem, per se. It's all up to the application... How to tell how much is stored depends on what application you used to store them in the first place.
# 3  
Old 11-20-2013
Oh really? I did not know that. All this time I'm thinking that a file is stored like a song on a regular cassette tape. Whereas if a song only lasts like three minutes or so, the remaining 57 minutes is still available. Obvioulsy, I'm speaking about a 60 minute tape cassette.

So when you mention application, are you asking about a ubackup or ubackups or am I out in left field all alone?
# 4  
Old 11-20-2013
Actually you're exactly right, but consider the implications.

An audio CD has tracks. You can command the CD player to jump to track 12 and it will do so, know how far it jumped, how much is left to play in that track, and where exactly the CD will end. It contains information on its contents... A cassette doesn't -- to find the end you have to listen to it. The 'end' might not even be silence, just old music you no longer care about, so you have to pay attention too.

Figuring this out is what a filesystem does for you and a tape doesn't. That often but not always becomes the tape application's job. It's also possible to just use a tape raw, with nothing but you keeping track of where its valid contents start and end.

By 'application', I'm asking exactly what you type or click to make a backup happen.
# 5  
Old 11-21-2013
Thanks for the file system explanation.

When I perform the backups, I use a different tape for every day of the week. For example, I'll use the same tape for Monday. I'll use another tape for every Tuesday. And, so on.

Most of the work that I do is through the console. I type:

su - ubackups

When prompted, I enter my password.

I'm then brought to the backup/restore menu. I enter my options to ensure I perfrom a backup to tape. Once I'm done with that, I then tar the file using the tvf options. I attempted to read the man pages for the tar options but that's like rubbing my sandpaper into my eyes.

Last edited by Scott; 11-21-2013 at 03:15 PM.. Reason: Could we please use code tags?
# 6  
Old 11-21-2013
Okay, third time lucky...

It would be useful to know what you did in that backup application, what you typed into tar, not just that you did so.

Unfortunately ubackups is not an application I am familiar with, I cannot find any reference to it on the internet, but hopefully your tar commandline will be more enlightening. 'tar' stands for 'tape archiver' and it's possible that most of what's happening is done by it.
# 7  
Old 11-21-2013

Once I'm done with the tape backup, I use:

tar tvf /dev/rmt/0

Last edited by Scott; 11-21-2013 at 03:15 PM.. Reason: Code tags
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