finding remaining space in Tape ( DAT)

[madhudeepan]

we are using DAT drive to take ignite backup,
how to identify the remaining space on that tape

[Johnson Punniyalingam]

This is difficult. I think the best way is if youre using fbackup / Backup software , it reports at the end of the backup;

total blocks written to output file /dev/rmt/2m: 54756166

[Michael Steele_2]

Hi

Ignite has two records of 2K and 10K or 2048 bytes and 10240 bytes.

A 4mm DAT tape holds 8 GB or 1024 bytes x 1024 x 1024 or 1024 MB or 1048576 KB

a) mt -f /dev/rmt/0m rew
b) mt -f /dev/rmt/0mn fsf 1 (* move forward one record past the 2K lif record *)
c) dd if=/dev/0mn of=/dev/null bs=10240

Will return with

XXXXX blocks in out

XXXXX * 10240K minus 1048576 KB minus 2K (* first LIF record *)

[Michael Steele_2]

PS WAG

[Steven Schweda]

> total blocks written to output file [...]

> XXXXX blocks in out

And if the drive does compression, then you
still know approximately nothing about the
remaining tape.

[Michael Steele_2]

Again, smartness. Do you see tape compression in the device? I'm using 0m as an example not c#t#d#BEST0m.

[Patrick Wallek]

>> I'm using 0m a

Potentially irrelevant. Some drives do compression internally no matter what you do from the OS side.

[Michael Steele_2]

Except that if compression is automatic then the total size of is also provided and then the 8 GB DAT tape will be 12 GB. So you just substitute the 12 GB.

All tape drives advertise their sizes.

[Steven Schweda]

> [...] I'm using 0m [...]

And who cares what _you_ are using?

And if a tape is written with compression, do
you think that the tape drive will read it
without compression, no matter which device
name you use?

> Again, smartness. [...]

Beats the opposite, I claim.

[Michael Steele_2]

And your personal motto says it all

"..Questions are a burden to others.."

Dude, you got some issues