Make recovery tape path name

[Ngoh Chean Siung]

Hi,

What is the difference between /dev/rmt/0mn & /dev/rmt/0m? What the n stands for? Which one to use during make_recovery?

regards.

[Michael Tully]

The 'n' stands for no-rewind. It is very much needed. The way it works is that the LIF is written to the tape in the first instance, so it is made bootable. It then creates a file marker, and goes to the next segment on the tape to create the system archive.

make_recovery is really extinct now, use make_tape_recovery

e.g. to create an ignite tape, only backing up /dev/vg00

# /opt/ignite/bin/make_tape_recovery -x inc_entire=vg00 -I -v -a /dev/rmt/0mn

[Con O'Kelly]

Hi

/dev/rmt/0mn means "no rewind"
You must use this with ignite backups.

Cheers
Con

[Ngoh Chean Siung]

Hi,

I think I have run make_recovery -A -C -d /dev/rmt/0m for quite some times but the backup is still successful. Any impact of not running with 0mn?

regards.

[Michael Tully]

You only think it is successful. What happens is that after the first part of the tape has been written, because your using a rewindable device (0m) the tape will rewind after the first segment and actually overwrite from the beginning of tape, making your backup pretty much useless as far as a full recovery is concerned.

You *MUST* use a non-rewindable device to get a good ignite backup.

[Ngoh Chean Siung]

Hi,

Currently I will do the make_recovery once every month. I am using 2 tape (A & B) for the rotation.

Let said I do the make recovery for Jun using tape A and if I specify with /dev/rmt/0mn, it means that the next time I do the make recovery, Jun make recovery will still exists or ...?

What I understand is make recovery will create the LIF first, followed by system files. Am I right?

regards.

[Michael Tully]

Once you have completed the make_tape_recovery, (LIF and system files) the tape will not rewind. However when you run the command the next time the tape will rewind to the beginning of the tape, so you will have only one backup per tape.

>> What I understand is make recovery will create the LIF first, followed by system files. Am I right?

Yes, that's correct. The LIF is created on segment 1 of the tape and the system files are on segment 2.

[Ngoh Chean Siung]

Hi,

>Once you have completed the make_tape_recovery, (LIF and system files) the tape will not rewind. However when you run the command the next time the tape will rewind to the beginning of the tape, so you will have only one backup per tape.

Above statement is having n, right?

But, if I don't put n, once the make recovery completed, the tape will rewind. Am I right? Then I think it is good as the LIF will always located at the beginning on the tape & it is good for restoration, right?

regards.

[Michael Tully]

1)

yes (/dev/rmt/0mn)

2)

yes

3)

yes (good restoration)

[Patrick Wallek]

The tape will rewind automatically when you eject it. So when you put it in to use it next time, the tape will be at the beginning and the LIF area will be at the beginning of the tape where it is supposed to be.

However, just to be on the safe side I put a

mt -f /dev/rmt/0mn rew

statement inside the script I use to create the tapes. That way I KNOW FOR SURE that the tape is at the beginning before I start the make_tape_recovery.

[Ngoh Chean Siung]

Hi,

I found below statement through man

-d destination
Specifies the device file of a DDS or DLT tape drive where the System Recovery Tape is to be created. A no-rewind device file is required. The default is /dev/rmt/0mn.

Questions:
1) Is n stands for no-rewind?
2) If yes, the tape will not be rewind after make_recovery completed if I specify /dev/rmt/0mn. Am I right?
3) What I understand from your feedback is the tape will be rewind after make_recovery completed without n or with n. Both are the same. Am I right?
4) During make_recovery restoration, I know the command is mt -t /dev/rmt/0mn fsf 1. Why here need n? (Because fsf is stands for forward space countfiles).
5) Just wonder is all the tape will be rewinded to the begining after the backup is finished (exp: fbackup, tar & ...)

regards.

[Mei Jiao]

Yes, n means no-rewind. When using make_recovery or make_tape_recovery, please using the device file /dev/rmt/0mn with n.

[Michael Tully]

1) 'n' stands for no-rewind
2) The tape will not rewind after the make_tape_recovery has completed.
3) The tape rewinds when you press the button for the tape to be ejected, not when the archive has completed. You must use the no-rewind device. (/dev/rmt/0mn)
4) Yes, you can fsf 1 (forward skip file) to recover files from the archive.
5) The tape does not rewind until you press the eject button, or run a rewind from command line. e.g.
mt -t /dev/rmt/0m rew

[Ngoh Chean Siung]

Hi,

Without n, tape will be rewinded to the beginning of the tape after make_recovery completed.

With n, tape will not be rewinded after make_recovery completed.

But, after we pressing the eject button, the tape will also rewind. So, why we still need to specify "no rewind" because it will be rewinded at the end also by pressing the eject button?

Why we don't want to rewind the tape after make_recovery completed? Is there any issue? I think it is good if the tape was rewinded because the LIF is at the beginning of the tape. So during restoration, we don't need to rewind the tape to the beginning to search for the LIF. Am I right?

regards.