Hao much tape have I used?

Hao much tape have I used?

[Paul Furness]

Can anyone tell me how to find out how full a tape is? Specifically, DLT
and LTO tapes which are in a robot. I have no problem loading the tapes
into the drive (using MTX) and mt works just fine - but after putting a
load of dumps on the tape, I need to know it the tape is actually full
or not. And of course, the tape drive uses hardware compression, so I
can't just add up the data dumped and subtract it from the capacity of
the tape because the compression is variable.

Any ideas / experiences with this would be appreciated.

P.



-- 
Paul Furness

Systems Manager

2+2=5 for extremely large values of 2.

Re: Hao much tape have I used?

[Mohammed Khalid Ansari]

Hi

I am using tar to take backup on to the tape. I want to know whether I 
have to enable the "compression" manually in tar or it is done by the 
hardware itself.

-- 

**************************************************************************

Mohammed Khalid Ansari                    Tel (res) : 0091-022-3051360
Assistant Manager II                          (off) : 0091-022-2024641
National Centre for Software Technology   Fax       : 0091-022-2049573 
8th flr,Air India Build. Nariman Point,   E-Mail    : khalid@ncst.ernet.in 	
Mumbai 400021.

Homepage : http://soochak.ncst.ernet.in/~khalid			  	  

**************************************************************************

On 8 Sep 2002, Paul Furness wrote:

> Can anyone tell me how to find out how full a tape is? Specifically, DLT
> and LTO tapes which are in a robot. I have no problem loading the tapes
> into the drive (using MTX) and mt works just fine - but after putting a
> load of dumps on the tape, I need to know it the tape is actually full
> or not. And of course, the tape drive uses hardware compression, so I
> can't just add up the data dumped and subtract it from the capacity of
> the tape because the compression is variable.
> 
> Any ideas / experiences with this would be appreciated.
> 
> P.
> 
> 
> 
> 

Re: Hao much tape have I used?

[Glynn Clements]

Mohammed Khalid Ansari wrote:

> I am using tar to take backup on to the tape. I want to know whether I 
> have to enable the "compression" manually in tar or it is done by the 
> hardware itself.

It depends upon whether you're referring to "hardware" compression
(which is performed by the tape drive), or "software" compression
(i.e. feeding the output from "tar" through "gzip" etc).

For hardware compression, you normally control whether compression is
performed by using the "mt" command prior to writing to the tape.

Software compression is performed either by using the appropriate
"tar" switches (e.g. "-z", "-Z", "--use-compress-program" etc), or by
manually piping the output from "tar" through the compression program
before writing it to the tape drive.

Using software compression for backups is generally considered a bad
idea, as a single error may render a substantial proportion of the
backup unusable. Hardware compression tends to have better
recoverability (but a lower overall compression ratio).

-- 
Glynn Clements <glynn.clements@virgin.net>

Re: Hao much tape have I used?

[Unix]

mt tell, tell you in which block of the tape are you located, so if you know 
how much blocks you tape has you can see how much tape is left.

On Sunday 08 September 2002 08:42, Paul Furness wrote:
> Can anyone tell me how to find out how full a tape is? Specifically, DLT
> and LTO tapes which are in a robot. I have no problem loading the tapes
> into the drive (using MTX) and mt works just fine - but after putting a
> load of dumps on the tape, I need to know it the tape is actually full
> or not. And of course, the tape drive uses hardware compression, so I
> can't just add up the data dumped and subtract it from the capacity of
> the tape because the compression is variable.
>
> Any ideas / experiences with this would be appreciated.
>
> P.

-- 
Luis Valencia