using time machine on a Sparse image

Just wondering if it is possible to restrict time machines use of my Ext HD by backing up the "backups.backupdb" onto a very large (600GB) sparse disk image?

i don't want to partition my Ext HD but i don't need months and months of backup data.

is this possible or is there another way.

thanks in advance

 

great really glad! thanks for the quick reply

i'll give it a go and post back with progress

 

OK!

more searching on google and i discovered that it is widely assumed to be impossible! and when i tried it it wouldn't work. after several attempts from various angles i returned to google seeking sympathy.

after ages i found this article:
http://nslog.com/2008/11/11/formatting_the_drobo_for_time_machine_backups

explaining how to use a command line:

hdiutil create -size 1024g -fs HFS+J -volname "Time Machine Backup" /Volumes/Mimzy/Bunny_0017f202b9ec.sparsebundle

this should of course be modified to your requirements e.g. change the path / size etc...

i couldn't get this to work but the author also mentions a piece of software called "time tamer". (his link to this is no longer useful but you can find it here http://support.drobo.com/app/answers/detail/a_id/610/~/drobo,-drobo-s,-drobopro,-drobo-b800i-support-for-lion-time-machine

i was afraid that it would only work for drobo machines but i gave it a go and i am currently backing up to the disk image now.


An IMPORTANT POINT!: time machine will not recognise the sparsebundle its self but if you put it on your Ext HD (at the top - not in a folder) then time machine will automatically write to it rather than the straight to the ext HD

i am still backing up but i will post when i know whether the backup is functioning correctly

hope this helps someone