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Which "space used" numbers to believe?

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I performed my first backup using the 30-day trial,. Based on what I already see I've ordered a boxed copy.

However, If the .tib file occupies 358.5 GB and the original files occupy 403 GB that isn’t much compression and I’m not doing much better than simply mirroring my C:\ drive to an external drive and not using backup software at all. Am I missing something?

DETAILS

I performed the backup of my boot drive with the target being a reformatted 2 TB USB drive. Things went well for the backup, but my curiosity lead me to check how much space was occupied by the backup files. I first did a right-click/"properties" in Windows Explorer and the returned window for the C:\ drive showed 403.5 GB used. I did the same thing for the backup drive and the window showed 344 GB used. Smaller than the original file space but larger than I expected.

Still in Win Explorer, I clicked on the "My Backups" folder of the backup drive and the right pane of the window displays in part Name (Boot Drive - Vista (C).tib) Type (Acronis TrueImage Backup) and Size (358,483,662 kb).

The "Disc backup" window of the ATIH software shows Source (403.5 GB of 455.7 GB used; estimated backup size 241.3 GB) and Destination (1862.87 GB of 1863.01 GB free).

So the estimated backup was 241.3 GB and the actual backup is 344 GB to backup the entire 403 GB of my C:/ drive if you believe the "properties" tab in WEx. or the space occupied by the .tib file is ~ 358.5 GB if you look at that file.

SUMMARY of C:/ backup file space:

• Properties tab for original C:\ drive = 403 GB
• Properties tab for backup (K:\) drive = 344 GB
• Right pane of Explorer window (.tib) = 358.5 GB

Anhang Größe
acronis.pdf 122.56 KB
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How much compression you get depends on what you are trying to compress. A lot of files today are compressed to begin with -- even Adobe Acrobat employs some compression. Also, jpgs and aac, mp3s, etc are strongly compressed in their native state, so don't expect any further compression for those files. The amount of compression isn't always or even often apparent from the file type, so estimating befgore hand how much compression will be achieved using any particular compression algorithm is an iffy business at best.

Also note that a backup file has some more info in it than just the files. When backing up, ATI creates a checksum every so many bytes and embeds the checksums in the backup file. This allows ATI to test whether the file has changed since it was created (validity). Since you can backup while using a pc, comparison to original files isn't a valid comparison and this is how ATI gets around that problem.

Also note that there will be more bytes used on a hard disk than just user files. You can read a lot more about these topics on Wiki, for example.

Thanks, Scott. Your explaination helps.

I guess that I was a little disappointed because years ago I used some software called "Go Back" (I think it may be a Corel product now) that wasn't really meant for backups but the resulting backed up file size was much smaller - maybe about 10% or less of the C:\ drive. But in retrospect I'll bet that it only copied and compressed the document/pic/spreadsheet, etc and not program or system files. Also, the 2 TB drive that I reformatted for my backup drive came with Seagate Replica software that was HORRIBLE. But it did produce a much smaller compressed image.

I'm learning. I'll read more on Wiki.

Thanks again.

GoBack recorded your changes to sectors, so that it could unwind them. This is something similar to what ATI does while backup up, tracking changes while you backup to that the backup can complete but you don't lose any changes on your hdisk. Windows Restore (the Vista & w7 versions) do something even more similar to GoBack, which is why your used space size on a vista or w7 system partition grows so large with continued use (it can actually double in size, not counting any programs you install).