Main Area and Open Discussion > General Software Discussion

How do incremental backup programs work?

(1/5) > >>

jgpaiva:
Ok, so as i know most people here know more about backup than i do, I'm interested in asking you 2 things:
If you change one bit in a 8GB file, how much space does the incremental backup take? does it add just a few kb, or the whole 8GB? More specifically, does the incremental backup work by whole files or byte by byte?
How about if you change the name of an 8GB file? Does it consider that as a new file, or is it smart enough to tell it's the same file with a new name?

Sorry, just another question: I know some backup programs (that do incremental backup) allow you to see the files you've backed up. How does that work? Do they come up on Windows Explorer (as a virtual drive or something) or do they use a sort of "Backup Explorer", a proprietary application that works similarly to WE but can only be used for backups?

Thanks a lot!

justice:
AFAIK,
Incremental Backup will back up the complete file if the file has changed, so 8GB. But if you have 1000 files which total 8GB then only those that have changed are backed up.
Block Level Incremental is "  A more sophisticated method of backing up changes to files is to only back up the blocks within the file that changed. This requires a higher level of integration between the filesystem and the backup software." which would only back up a few KB.

Your other questions depend on the backup software that you're looking at, for example SyncToy (not a backup program really) and SFFS keep a database of changes so that it knows you renamed your 8GB file and can do the same on the other end without uploading anything, most other programs do not. Also some programs such as Jungle Disk that I wrote about create a network mapped drive to make their files available, others don't. This usally depends on whether or not the final backup is filebased or image based (ie, the whole backup is one or more split archives or whether they are folder structures in the file system). Hope that helps

tomos:
AFAIK incremental backup usually means they will back up the files that have changed (again) and ignore the files that havent
That usually means full file is backed up

Then there's partial file update (probably known under different names) which is used with synching -
the changed "bit" in your original 8GB file gets updated in the synched file
Obvious problem here being if your file corrupts you have no backup as such
SFFS does this
SFFS keeps track of files if moved (says it does anyway) but not sure what happens if the name is changed...

thats about my limit [Justice got in ahead of me there...]

mouser:
Sorry, just another question: I know some backup programs (that do incremental backup) allow you to see the files you've backed up. How does that work? Do they come up on Windows Explorer (as a virtual drive or something) or do they use a sort of "Backup Explorer", a proprietary application that works similarly to WE but can only be used for backups?
--- End quote ---

Some programs mount the backup file as a virtual drive that shows up in explorer (Acronis for example) and some use their own backup explorer (Genie backup for example).  And still other simply use a standard archive file format for backup so you can open them in your own tool.

Perry Mowbray:
I'll answer this one...

Sorry, just another question: I know some backup programs (that do incremental backup) allow you to see the files you've backed up. How does that work? Do they come up on Windows Explorer (as a virtual drive or something) or do they use a sort of "Backup Explorer", a proprietary application that works similarly to WE but can only be used for backups?
-jgpaiva (June 17, 2008, 05:47 AM)
--- End quote ---

It depends on how the actual software stores the backup.

For example, Backup4All gives you the option of zipping the files or not. You can browse the backups using the file system, though if you are keeping versions it can get a little confusing (better to use B4A). From memory SyncBack is similar.

FirstDefense though stores it's data in an archive file of some description that I've never tried to access through the filesystem.

Just to reinforce Justice's explanation:
Incremental refers to the Backup as a whole, not the individual files being backed up.
An incremental backup is a backup method where multiple backups are kept (not just the last one). These backups will be incremental if each original piece of backed up information is stored only once, and then successive backups only contain the information that changed since a previous backup.-WikiPedia
--- End quote ---

Navigation

[0] Message Index

[#] Next page