Confused about backups sizes - PBS vs SMB

[chudak]

Hello,

I am backing up my CTs/VMs to PBS and SMB storage targets.

Back-up size for CT (ubuntu):

on PBS is ~19GB vs SMB ~4GB

and for a VM (windows):
on PBS is ~120GB vs SMB ~55GB

I would expect to have that vise verse.
Why such a difference?

I am sure there is a good explanation for this.

Happy Holidays!

 

[Dunuin]

PBS can't know how big a single backup is because everything is deduplicated. So for single backups PBS will only show the size of the complete (non sparse) data of the guests virtual disk on the host. So if you got a 100GB virtual disk with 20GB data on it, PBS will report it as 100GB even if it might only consume 100MB on the datastore after compression and deduplication.
So you can only see the real size of all backups together. In PBS look at the logs of the last "Garbage Collect" task. There you will find something like this:

2021-12-05T07:47:15+01:00: Original data usage: 3.498 TiB
2021-12-05T07:47:15+01:00: On-Disk usage: 85.784 GiB (2.40%)

In my case my whole datastore with all the backups combined will store 3.498 TiB of virtual disks but these only consume 85.784 GiB of space, so PBS saves me 97.6% of the space.

 

[chudak]

PBS can't know how big a single backup is because everything is deduplicated. So for single backups PBS will only show the size of the complete (non sparse) data of the guests virtual disk on the host. So if you got a 100GB virtual disk with 20GB data on it, PBS will report it as 100GB even if it might only consume 100MB on the datastore after compression and deduplication.
So you can only see the real size of all backups together. In PBS look at the logs of the last "Garbage Collect" task. There you will find something like this:

2021-12-05T07:47:15+01:00: Original data usage: 3.498 TiB
2021-12-05T07:47:15+01:00: On-Disk usage: 85.784 GiB (2.40%)

In my case my whole datastore with all the backups combined will store 3.498 TiB of virtual disks but these only consume 85.784 GiB of space, so PBS saves me 97.6% of the space.

Thanks in my case I see:

2021-12-24T11:35:00-08:00: Original data usage: 1.537 TiB
2021-12-24T11:35:00-08:00: On-Disk usage: 391.821 GiB (24.89%)

 

[slatts]

I'm also backing up to SMB storage so ran into this question as well. Thank you for the answer . It would be nice if On-Disk usage could be added to the UI in the future.

 

[tcabernoch]

Gawd. I would swear it was in the UI. In fact, the only place I can find that info is in the final lines of the GC log.

2025-04-26T14:00:28-04:00: Original data usage: 12.303 TiB
2025-04-26T14:00:28-04:00: On-Disk usage: 1.998 TiB (16.24%)

And that means I spend way too much time reading log files ...