All the replies are correct and they are the reasons why incremental forever is better and need less time to restore. Maybe a real example can help you. I had more than 8 years in operations and I can say that TSM is much better. I had the following experience:
Some "great" application developer create files using date as a part of the file name. Some of these files are vital e.g. price files, but some are not important, e.g. temp working or log file for trace. The backup job needs to backup all the files. The disk crash on Friday and we need to restore the files. For traditional FULL + INCREMENTAL, I need to restore all these date specific files which are useless, so it is a waste of time to restore them. The bad news did not stop here. I found out some of these date specific files are huge ("smart" developer write everything to log file, so that they are able to trace if there is problem). The application will delete these files in a "day-end" job to reclaim the disk space. However, FULL + INCREMENTAL will restore all these huge temp files. As a result, I ran out of disk space when I restore the daily incremental. So I had to delete those temp files, restore the second incremental, delete temp files, restore the third incremental,... until incremental of Friday morning. The total time to restore include this manual delete files process that people often ignore and forget. For TSM, it will not restore these intrim temp files and only restore the files I need using point-in-time restore feature. FULL + INCREMENTAL is not able to do. Therefore, it is much better. Hope this example can help you to explain and understand why TSM is better. Thanks & Regards William |---------+----------------------------> | | Gianluca | | | Mariani1/Italy/IB| | | [EMAIL PROTECTED] | | | Sent by: "ADSM: | | | Dist Stor | | | Manager" | | | <[EMAIL PROTECTED]| | | .EDU> | | | | | | | | | 05/03/2003 22:47 | | | Please respond to| | | "ADSM: Dist Stor | | | Manager" | | | | |---------+----------------------------> >--------------------------------------------------------------------------------------------------------------------------------------------| | | | To: [EMAIL PROTECTED] | | cc: | | Subject: Re: progressive backup vs. full + incremental | | | | | >--------------------------------------------------------------------------------------------------------------------------------------------| 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) [EMAIL PROTECTED] ---------------------------------------------------------------------------------------------------- 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 <[EMAIL PROTECTED] HMARK.COM> To Sent by: "ADSM: [EMAIL PROTECTED] Dist Stor cc Manager" <[EMAIL PROTECTED] bcc ST.EDU> Subject progressive backup vs. full + 05/03/2003 incremental 15.21 Please respond to "ADSM: Dist Stor Manager" 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 [EMAIL PROTECTED] (717)975-8338