Radically Different Size of Backups

I just asked the question about a lost RTF file and have been exploring locating backups both from within DTPro and in my Documents file. The Documents file has only one DT database listed – I assume the current version. I have not been able to find the other recent backups in the Documents file.

Various version of backups used to be listed in the User Library with DT before the Pro version.

Now, the only versions of backups I can see are under Tools, when I click on “Restore Backup …”

Currently, my list called “Select Backup” lists 5 options, with the sizes from most recent:

98.0 MB
102.5 MB
97.7 MB
409.4 MB
85.2 MB

The top two backups date from after DT crashed and I asked DT to Rebuild the database.

I’ve noticed similar differences in backup sizes in DevonThink, before the Pro version.

What could account for the huge differential in size of backups? If anything, I’ve mostly added files since the date of the very large backup; I deleted just a few. Does this mean I lost 3/4 of my files between three days ago and today? It doesn’t seem so just looking at the folder and file names and numbers and random checking to see if the actual files are still there.

Also, a related question: When I Get Info on my DT Pro database in the Documents file, it tells me the database is 923.9 MB on disk. Why is there such a difference between the backup size and the actual file size?

I’d feel much more secure using this program if there were good reasons for these differentials.


There are good reasons:

[1] Apparent increase in size of a database: In use, especially with additions and edits, the database begins to ‘spread out’. Running Backup & Optimize will reduce the size of the database (optimize it) in such cases. This can also improve performance.

[2] When you check the size of the database package in the Finder, it obviously adds up the size of the database, its Files folder, and your 5 Backup folders. That’s why the package takes so much storage space on your hard drive. If you were to do an external backup using DT Pro’s Scripts > Export > Backup Archive, the external backup will require much less disk space. It will include only your database and the Files folder, and then compress the package into a zipped file (which will be uncompressed when double-clicked). If you were to start using this backup, it will add the number of backup folders specified in DT Pro’s preferences, and start to grow again as backups are done.

Thanks for another clear and prompt explanation. This is very reassuring.

When offered a choice of apparently different sized backups, should I select the largest one if I want to “Restore Backup,” or the most recent, or doesn’t it matter?



Assuming your most recent backup is of an error-free and complete copy of your database at the time it was made (which it should be, I would hope), choose the most recent. The most recent one will be named “Backup”, the next more recent will be named “Backup0”, one still older will be named “Backup1” and so on.

If you experience unfixable database errors, your choice would be between restoring a backup, or rebuilding the database. At that point I would close DT or DT Pro and make a copy of the database to a different location (in case anything goes wrong). Then I would launch DT/DT Pro and choose Restore Backup, choosing the most recent one. Run Tools > Verify & Repair. If there are no errors, or the errors can be fixed by running Verify & Repair until no errors are found, you should have a sound database. The only problem is that you would lose any additions or edits done after that backup was made. If the newest Backup is corrupted, you might try the next oldest, with a still greater potential of losing data added after that backup.

Another approach would be to Rebuild the database. Once again, there’s a possibility that you might lose some contents that had become corrupted.

That’s why I recommend making reasonably frequent external backups while you are sure that your database is running properly. Example: With DT/DT Pro quit, copy (Option-drag) your database to another location, preferably an external drive.

And, of course, make an “internal” backup after adding lots of new content, doing edits, etc. so that you minimize the risk of losing your time and effort. Run Verify & Repair, then Backup & Optimize. I do this manually, rather than depend on scheduled backups.

It has been many months since I’ve encountered a database problem, and I happened to have backed up the database both internally and externally just before that, so I really didn’t lose any work. Another application crashed the operating system, requiring a forced shutdown, and damage to my DT Pro database (I’ve been running alphas and betas of DT Pro for almost a year and a half). No harm done. That’s why I recommend backups!

Christian, the architect of the database, recommends an occasional Rebuild to keep it at its peak condition. This would be recommended if your database dates back a year or more and has never been rebuilt. It would also be recommended if the database advises you to do so.

Thank you. I’ve already learned the hard way to build external backups into my routine, and I’ll add the info on “Restore Backup” to my repertoire.

Perhaps, as a suggestion, the kind of detailed maintenance information you’ve been providing me could be part of future editions of the tutorial or the manual, or be assembled an posted in a special place on the website. I suspect there are many others like me who don’t know what questions to ask or what to search for and, thus, fail to find such useful, fundamental information in the support files.

As you may remember from my initial questions a few months ago, the first problem I had with DT was caused by an external drive (that I use for backups) that was corrupted and corrupted my entire hard drive in turn, including, of course, my precious DT files. If it were not for the wonderful people at the Apple Store who backed up my whole computer for me and cleaned out my whole disk drive, tested to locate the corrupt files, and then restored the remaining healthy files back onto my drive, I never could have recovered from that on my own.

So, … Do you have a maintenance routine similar to that for computers that you use for external drives?

FYI. I have a SmartDisk Firewiire 60 and a SmartDisk Firewire 80.

Thanks for all your help.