Does Time Machine use a differential/delta file compression when copying files ?

Unless the single file database uses a sparse bundle type scheme, it is treated as a single file and any change will require a full copy of that database.

The capability to work with Time Machine is already implemented in the Sparse Bundle storage format. You need to request that your App developers build their monolithic storage formats compatible with Time Machine.

If others are also interested in such a feature, you’re welcome to vote for it.

Polls and petitions violate the terms of use of this forum.

You should exclude the virtual disk file from Time Machine backups. There's no way it can be backed up efficiently. Instead, back up the contents from within the guest OS, using native backup tools.

Really no reason to. The programs needing that kind of storage just need to implement a sparse bundle disk image, or any other file striping method.

Time Machine doesn't do any file comparison at all.

The OS has a daemon that tracks every file system change (fsevents). The changes are stored in a database and Time Machine uses that database to decide what gets backed up.

There really isn't a way to implement those features as the program doesn't do any file comparison at all.

ohault wrote:

We are talking here about a network protocol that will be used by Time Machine on OSX to communicate with a Time Capsule, not the way bits are stored on disks.

No, it is about the way bits are stored on disks. Time Machine is complex enough as it is.

If you are using a virtual machine so much that you really need it backed up, perhaps you should consider using that operating system. Otherwise, you can configure your VM software to store files in your Mac home directory where Time Machine will back them up.

ohault wrote:

I would like to use Time Machine to backup to a MacBook Air but that computer is using a Virtual Machines store in a single file of 50 GBytes...

Is that really a good idea? If you have Time Machine running automatically (I don't), it will undoubtedly be backing up the VM while it's in use. The VM file (which, at least in VMware Fusion) is really a bunch of smaller component files, which would be in a constant state of flux, so as the TM backup proceeded, the VM state at the end of the backup would be different from its state at the beginning and the component files wouldn't align time-wise. As a result, wouldn't the VM file restored via TM run the risk of being corrupted?

FatMac\>MacPro wrote:

ohault wrote:

I would like to use Time Machine to backup to a MacBook Air but that computer is using a Virtual Machines store in a single file of 50 GBytes...

Is that really a good idea? If you have Time Machine running automatically (I don't), it will undoubtedly be backing up the VM while it's in use

Time machine does not backup files that are open.

Csound1 wrote:

FatMac\>MacPro wrote:

ohault wrote:

I would like to use Time Machine to backup to a MacBook Air but that computer is using a Virtual Machines store in a single file of 50 GBytes...

Is that really a good idea? If you have Time Machine running automatically (I don't), it will undoubtedly be backing up the VM while it's in use

Time machine does not backup files that are open.

So the OP's VM would only be backed up by TM if the Mac was running but the VM was not?

Yup, much better to make snapshots.

Csound1 wrote:

Yup, much better to make snapshots.

While that would offer a "retreat" position (I find that one of the great features of VM's over a real PC), does that qualify as a true backup?

What do you categorize as a 'true' backup

Csound1 wrote:

What do you categorize as a 'true' backup

The VM file or the Mac gets trashed and you need a copy of the VM from somewhere else. So you go to your backup.