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Time stamps on sessions on a DVD backup.

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  Time stamps on sessions on a DVD backup. peter@easthope.ca - 2023-08-12 23:10 +0200
    Re: Time stamps on sessions on a DVD backup. "Thomas Schmitt" <scdbackup@gmx.net> - 2023-08-13 00:10 +0200
      Re (2): Time stamps on sessions on a DVD backup. peter@easthope.ca - 2023-08-13 01:00 +0200

#260888 — Time stamps on sessions on a DVD backup.

Hello again,

Here a session of a backup archive is written to a DVD.

xorriso -for_backup -dev /dev/sr0 \
  -update_r . / \
  -commit \
  -toc -check_md5 failure -- \
  -eject all
 
This command gives the contents of a DVD.
  xorriso -dev /dev/sr0 -toc

TOC layout   : Idx ,  sbsector ,       Size , Volume Id
ISO session  :   1 ,         0 ,    678303s , ISOIMAGE
ISO session  :   2 ,    716368 ,     13376s , ISOIMAGE
ISO session  :   3 ,    737600 ,    816699s , ISOIMAGE
  ...

Session time stamps would help when recovering from a 
storage failure.  Eg.

Date        TOC layout   : Idx ,  sbsector ,       Size , Volume Id
2023-07-23  ISO session  :   1 ,         0 ,    678303s , ISOIMAGE
2023-07-29  ISO session  :   2 ,    716368 ,     13376s , ISOIMAGE
2023-08-06  ISO session  :   3 ,    737600 ,    816699s , ISOIMAGE

Can the current xorriso include session timestamps?  In the manual I 
see file timestamps mentioned.  Not session timestamps.

Thx,                                   ... P.

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#260890

Hi,

peter@easthope.ca wrote:
> Session time stamps would help when recovering from a
> storage failure.  Eg.
>
> Date        TOC layout   : Idx ,  sbsector ,       Size , Volume Id
> 2023-07-23  ISO session  :   1 ,         0 ,    678303s , ISOIMAGE
> 2023-07-29  ISO session  :   2 ,    716368 ,     13376s , ISOIMAGE
> 2023-08-06  ISO session  :   3 ,    737600 ,    816699s , ISOIMAGE
>
> Can the current xorriso include session timestamps?  In the manual I
> see file timestamps mentioned.  Not session timestamps.

Currently only the creation time of the loaded session is in reach:

  $ xorriso -indev /dev/sr0 -pvd_info
  ...
  Creation Time: 2023081220110500
  ...

You would have to load each session and inquire it:
  $ xorriso -load session 1 -indev /dev/sr0 -pvd_info
  ...
  Creation Time: 2023072920104300
  ...

I encode the time in the volume id together with an id of the backup
script (here "HOME_Z"):

  xorriso \
    ... \
    -dev /sr0 \
    ... \
    -volid HOME_Z_"$(date '+%Y_%m_%d_%H%M%S')" \
    ...

The backup medium then bears a -toc like:

  TOC layout   : Idx ,  sbsector ,       Size , Volume Id
  ISO session  :   1 ,        32 ,   1213035s , HOME_Z_2023_07_29_220901
  ISO session  :   2 ,   1213088 ,     19527s , HOME_Z_2023_07_30_223447
  ISO session  :   3 ,   1232640 ,     17993s , HOME_Z_2023_07_31_214713
  ...
  ISO session  :  12 ,   1403136 ,     19367s , HOME_Z_2023_08_10_223506
  ISO session  :  13 ,   1422528 ,     15773s , HOME_Z_2023_08_11_222313
  ISO session  :  14 ,   1438304 ,     16758s , HOME_Z_2023_08_12_221015

Having an id for the backup script makes it possible to ensure that the
script is not applied to the medium of a different backup script.
Before loading the youngest session by -dev, i set the constraint

  -assert_volid 'HOME_Z_2*' FATAL \

which will let the next -dev command fail if the volume id does not match
the pattern 'HOME_Z_2*' or is (pseudo-)blank.


Have a nice day :)

Thomas

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#260893 — Re (2): Time stamps on sessions on a DVD backup.

    From: "Thomas Schmitt" <scdbackup@gmx.net>
    Date: Sun, 13 Aug 2023 00:08:23 +0200
> You would have to load each session and inquire it:

OK, thanks.

> Having an id for the backup script makes it possible to ensure that the
> script is not applied to the medium of a different backup script.

Good, thanks,                     ... P.



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