ITEM: N1836L

Wants to know the difference btw ver2 & ver3 sysback

Question:

Lee, Please call John back I am sending him a fax of info about the
changes in ver2 vs ver3 and a DEMO copy of sysback, but he is having
problems doing raw logical backup w\\ ver2.

Response:

Customer is having problems in version 2 of making raw lv backups
Here are some methods to doing this until you bug ver 3 of sysback.

With ver 3 you have the mklvback command that will backup a raw lv
and allow that data to span multi tapes.  You can't do that with
the methods I am showing you below.


METHOD 1  SKIPPING THE CONTROL BLOCK

Here is how to make a backup of a raw logical volume.
In the examples below you must skip over the control block (backup and restore).
If you don't skip over the control block unpredictable things may happen. 

( For 8mm and 4mm or anything that works best with block size of 1024)

1.  chdev -l rmtx -a block_size=1024
2.  dd if=\ of=/dev/rmtx ibs=512 obs=1024 skip=1 conv=sync

To restore

3.  dd if=/dev/rmtx of=\ ibs=1024 obs=512 seek=1 conv=sync 

( For 1/4" and 9trak or anything that works best with block size of 512)

1.  chdev -l rmtx -a block_size=512
2.  dd if=\ of=/dev/rmtx bs=512 skip=1 conv=sync

To restore

3.  dd if=/dev/rmtx of\ bs=512 seek=1 conv=sync

 NOTE:   If the backups are spanning more than one tape then the
         dd command will not work.  The only other method is to use
         sysback/6000 version 3.  This will allow the user to do backups of
         raw lvs over multi tapes.


============================================================================
============================================================================
============================================================================
============================================================================

2.  NOT SKIPPING OVER THE CONTROL BLOCK METHOD
( For 8mm and 4mm or anything that works best with block size of 1024)

1.  chdev -l rmtx -a block_size=1024
2.  dd if=\ of=/dev/rmtx ibs=4096 obs=1024 conv=sync

To restore

3.  dd if=/dev/rmtx of=\ ibs=1024 obs=4096 conv=sync

( For 1/4" and 9trak or anything that works best with block size of 512)

1.  chdev -l rmtx -a block_size=512
2.  dd if=\ of=/dev/rmtx obs=512 ibs=4096 conv=sync

To restore

3.  dd if=/dev/rmtx of\ ibs=512 obs=4096 conv=sync

 NOTE:   If the backups are spanning more than one tape then the
         dd command will not work.  The only other method is to use
         sysback/6000 version 3.  This will allow the user to do backups of
         raw lvs over multi tapes.

============================================================================
============================================================================
============================================================================
============================================================================

3  METHOD: USING COMPRESSION
(Using 8mm or 4mm)
cat /dev/\ | compress | dd of=/dev/rmt0 ibs=4096 obs=1024 conv=sync

To restore
dd if=/dev/rmt0 ibs=1024 obs=4096 conv=sync | zcat | dd of=/dev/\ bs=4096 
conv=sync    
   


Response:

Response:

  Customer tried the above solution and after 5 hours it failed with
  a I/O error.  Which could mean there is a bad tape, bad spot on the
  disk or bad scsi cables  it is hard to tell.  There are not errors
  in the errpt.  I am sending out the demo version of sysback ver 3
  so he could try using the mklvback command.

  Try this:
  make a jfs file system
  fill it up to about 90%
  umount
  Use on the of the dd commands from above to back it up
  rmfs the file system
  recreate it with the same size and name
  restore the data


Response:

Response:

  Customer just wanted some docs with the sysback.  I explained
  with the demo version the docs are in the /usr/lpp/sysback
  directory.



Support Line: Wants to know the difference btw ver2 & ver3 sysback ITEM: N1836L

Dated: October 1994 Category: N/A

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