Backing up sparse files ... VM's and TrueCrypt ... etc

[Tom Metro]

Edward Ned Harvey wrote:
> For whatever reason, tar performance is horrible in cygwin windows...

There are several "native" ports of tar, including:
http://unxutils.sourceforge.net/

One of these might perform better.


> Problem is ... it takes so long to send the whole file, I'll only
> back up once a month or so.

If you have adequate space on the target system, you could always use a 
hack with tar to "de-sparse" the file, and then incrementally back it up 
using some other tool, like rsync.

tar -cf - /path/to/sparse | gzip --rsyncable > sparse.tgz

(You'll need a gzip port with the --rsyncable patch too.)


> Do you successfully, frequently, efficiently, backup sparse files via rsync,
> including incrementals?

Nope. I don't think I've tried rsync with sparse files.


>> How about describing how you are using it?
> 
> It's been a while, I would have to repeat it now in order to remember how it
> was done.  I'll do it, if there's any good reason to believe it'll help ...

It may not be worth while, if you're confident you were using rsync in 
the optimal way. But it's common to see rsync misapplied, and easy to 
do. In this case with sparse files, I could see additional scenarios in 
which it might not work as expected.

For example, if you ran rsync on the file server, without a daemon on 
the client machine, two things would happen: 1. rsync would have to read 
the entire file via the network file system to look for changes, and 2. 
the "sparseness" may get lost if rsync is seeing the file through a 
network file system.

If you were running rsync on both client machine and file server, and 
weren't using any network file system paths in your rsync command lines, 
then you were probably doing it right.

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/