Progressive incremental backs up only new or changed files.  during the
initial backup the client  backs up all eligible files of course(full
backup). Subsequently, files are backed up again only if they are new or
have changed since the last backup. In TSMs case, a pointer to each version
of every file for every client is kept  in the database , so there is no
need for another full backup.
When  you  need to restore, you can choose the specific version of the file
or  point-in-time  to  restore,  and TSM will restore only  that particular
file or files. The approach used for full + incremental backups (NetBackup)
requires  an  initial  full  backup,  followed  by  regular  incremental or
differential  backups (usually once a day), with the complete cycle needing
a  full  backup  to  be  repeated on a regular (usually weekly) basis. This
backup  method  results in redundant weekly full backups of files that have
not  changed,  wasting  both  network  and  media resources. The multi-step
restore  process in this approach requires the software to restore the last
full  backup,  then to restore  incremental or differential backups  on top
of  that   in  order  to  recover the latest version of a file or an entire
system.  This  methodology  not  only involves restoring more data, it also
means  more  tape  mounts  and  tape  positioning and consumes more network
bandwidth all of which amounts to having longer restore times.



Cordiali saluti
Gianluca Mariani
Tivoli TSM Global Response Team, Roma
Via Sciangai 53, Roma
 phones : +39(0)659664598
                   +393351270554 (mobile)
gianluca_mariani AT it.ibm DOT com
----------------------------------------------------------------------------------------------------

The Hitch Hiker's Guide to the Galaxy says  of the Sirius Cybernetics
Corporation product that "it is very easy to be blinded to the essential
uselessness of  them by the sense of achievement you get from getting them
to work at all. In other words ? and this is the rock solid principle  on
which the  whole  of the Corporation's Galaxy-wide success is founded
-their fundamental design flaws are  completely  hidden  by  their
superficial design flaws"...


                                                                           
             Joni Moyer                                                    
             <joni.moyer@HIG                                               
             HMARK.COM>                                                 To 
             Sent by: "ADSM:        ADSM-L AT VM.MARIST DOT EDU                 
  
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             <ADSM-L AT VM DOT MARI                                           
bcc 
             ST.EDU>                                                       
                                                                   Subject 
                                    progressive backup vs. full +          
             05/03/2003             incremental                            
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Hello everyone!

I was wondering why the full + incremental would result in a longer restore
time than the progressive backup methodology?  From several co-workers
point of view they thought that it would be quicker on the full +
incremental because you wouldn't have to go back to the beginning backups
of the file and restore all of the incrementals, you would just go back to
the most recent full backup and apply the incrementals after that point.
When I went to explain the reasoning behind this, I had some problems
understanding the concept myself, so I was hoping someone could explain
both methods and why they differ in restore time and why progressive is
better than the full + incremental.  Thank you so much for any help you can
lend on this matter!



Joni Moyer
Systems Programmer
joni.moyer AT highmark DOT com
(717)975-8338