[Box Backup] I have the fear....

Per Reedtz Thomsen boxbackup@fluffy.co.uk
Tue, 13 Mar 2007 23:52:34 -0700

On 3/13/07 4:25 PM, Chris Wilson wrote:
> Hi Per,
> On Tue, 13 Mar 2007, Per Reedtz Thomsen wrote:
>>>  I agree with you and Martin that this is worthwhile, however I 
>>> think it's
>>>  worth adding support for the other options given that not all 
>>> platforms
>>>  support change notifications (does BSD or MacOS X?)
>> On OS X filesystem notifications are supported. For example spotlight 
>> uses them to index new and changed files, as they happen.
> Do you happen to know how this is implemented or used (how we can add 
> support for it in bbackupd)?
You listen to /dev/fsevents, and read off that device all the changes 
made to files across the machine. 
http://greenearthcommons.org/rian/gfslogger/ has a sample implementation 
that uses it.

IMO this is the way to go. Pick the events that bbackupd is interested 
in, and back them up. No need to scan the disk for changes. If I'm not 
mistaken, this is also the approach that Apple's 'Time Machine' backup 
solution uses.

It's important to note that this is a 'private' API, and that it may 
change between OS X versions; It requires root to use it (which is not a 
problem for bbackupd); it *could* have an adverse impact on Spotlight 
http://lists.apple.com/archives/darwin-kernel/2005/Sep/msg00030.html and 
http://www.kernelthread.com/software/fslogger/ have some more info on this.

I don't think that Box using this API would strain Spotlight beyond its 
breaking point, given that Time Machine is using it too.


Per Reedtz Thomsen | Reedtz Consulting, LLC | F: 209 883 4119
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