Why does Time Machine create a sparsebundle on networked drives?

[rbpeirce]

It creates individual files on attached drives. Why can't/doesn't it do that on drives attached to other computers on the network? I have both and have never seen an explanation.

 

[MacInWin]

Sparsebundle saves network traffic. It's compressed. That is the rationale for that, back when it was done. Today's networks are faster, so perhaps it's not needed, which may well be why Apple has changed from sparsebundles to snapshots for backups.

 

[rbpeirce]

So you're saying Time Machine can access a sparsebundle directly without actually opening it? I didn't think that was possible but it would make sense.

 

[MacInWin]

No, that is not what I said at all. What TM does is to open the sparsebundle, make the changes from the backup as usual to the backup and then close it.

 

[rbpeirce]

How is that faster than just making the change to a regular Time Machine backup?

 

[IWT]

How is that faster than just making the change to a regular Time Machine backup?

I think Jake kind of gave you this answer in post #2

In the past, when internet connections were much slower and where many Mac users had modest WiFi download speeds, Apple devised a system that would compress data when one did a TM backup. As mentioned before, this used sparsebundles which created internal links so that any additions to data from one BU to the next could be handled in the shortest time possible.

As WiFi and internet speeds increased over the years, it became less of a burden to prepare TM backups without compression and it opened up different formats which were faster & more efficient.

For example, in the past, a TM EHD was formatted Mac OS Extended (Journaled).

Nowadays, a much more efficient and faster option is available by formatting the EHD as APFS (Case-sensitive). This came about because APFS is designed for SSDs and all recent Macs have an SSD as their main drive and it is formatted APFS. Thus copying data from the Mac's SSD to a TM EHD also formatted APFS is faster & more robust.

HTH

Ian

 

[rbpeirce]

He said the sparsebundle is compressed. OK, but that just takes up less disk space. Is the traffic to and from it also compressed? If so, then I understand why Apple might take this approach.

 

[MacInWin]

Is the traffic to and from it also compressed?

Yes. That is what I said. What is transported over the internet is sparsebundle. It is "opened" to be modified by TM on the drive (not expanded, opened) and the compressed data added, then "closed" again.

 

[rbpeirce]

Yes. That is what I said. What is transported over the internet is sparsebundle. It is "opened" to be modified by TM on the drive (not expanded, opened) and the compressed data added, then "closed" again.

Thanks. That makes sense.