ReverseDelta is technology developed by Altaro Software that enables Oops!Backup to only save the changes between each version of a changed file, rather than backing up the whole file every time it is changed. This means that keeping multiple backup versions will require less space on your backup drive. What distinguishes ReverseDelta from other delta technologies? At Altaro we listened to what users felt was the main concern about delta files. The problem is that in the event of heavy data loss, the version of a file you are most likely to need is the latest one. Many users are apprehensive if this version may need to be rebuilt from an older version and one or more delta files. With ReverseDelta, the latest version of a file is always made available in its entirety and not as a delta file. This means that if you require the latest version of a file, it is possible to access it directly from your backup drive without having to rebuild the file from delta files. The delta files are only used if you want to build a previous version of the file, building one delta file at a time for each version as you travel back in time in the reverse direction. ReverseDelta is recommended for large files that change often, such as Outlook PST files or database backup files. How do I choose when to keep a full copy of the files? In the Advanced Settings window in Oops!Backup, there is an option to keep a full copy of a file every X versions. What does this mean? Let's say you have a large file, say 1GB, which changes all the time and needs to be backed up every hour. The first backup is for example at 9am. When you back up that file the first time, it is simply copied over to the destination. At 10am, it is copied over again, and at 11am again and so on. So you have 3 full versions on your backup drive, 9am, 10am, and 11am... That would mean 3GB in three hours... So Oops!Backup makes delta files of the OLDER files (9am and 10am) so that your latest (11am) is available as a full file. The delta file is usually much smaller (a few MB). If you choose "keep full file every 30 versions" means that every 30 backups, the delta file is not taken, so that you never have more than 30 delta files to rebuild if you need to restore a file. Let's say you set this setting to "5". The picture would look like this: -- Full file 10pm (Latest, 1GB) -- delta 9pm -- delta 8pm -- delta 7pm -- delta 6pm -- Full file 5pm (1GB) -- delta 4pm -- delta 3pm -- delta 2pm -- delta 1pm -- Full file 12pm (1GB) etc.. etc. If you need to restore the 2pm file, then you need to start from the 5pm full file, add on the 4pm delta, 3 pm delta and finally, the 2pm delta. These steps take some time, so this setting ensures that you are never too far away from a full file. This of course happens in the background and is totally abstracted from the user. |