Back up of already snapshoted folder in another back up is slow

[enboig]

I have a "dockers" folder where I do backup ups regularly. The structure is:

• /mnt/dockers
• /mnt/dockers/app1
• /mnt/dockers/app2
• /mnt/dockers/app3
• /mnt/dockers/app...

Sometimes, when upgrading an app, I make a backup of "/mnt/dockers/appX"; if everything works fine, after some days I delete this snapshot.

I observed that, despite data already backed up in "/mnt/dockers" snapshots, if there is no previous snapshot of "/mnt/dockers/appX" it takes a long time.

Shouldn't cache avoid this? All files appear as new despite most of them are in

First bakcup:

# time rustic backup "${PWD}" --label=this
[00:00:02] reading index...               ████████████████████████████████████████         83/83                                                                                                                                
[00:00:00] getting latest snapshot...     ████████████████████████████████████████        226/226                                                                                                                               
[01:50:02] backing up...                  ████████████████████████████████████████ 702.85 GiB/702.85 GiB 109.00 MiB/s (ETA -)                                                                                                   Files:       95318 new, 0 changed, 0 unchanged
Dirs:        6380 new, 0 changed, 0 unchanged
Added to the repo: 11.0 MiB (raw: 27.7 MiB)
processed 95318 files, 702.9 GiB
snapshot fc7178fe successfully saved.

real    112m24,578s
user    115m27,341s
sys     13m26,514s

Second snapshot:

# time rustic backup "${PWD}" --label=this
[00:00:02] reading index...               ████████████████████████████████████████         85/85                                                                                                                                
[00:00:00] getting latest snapshot...     ████████████████████████████████████████        227/227                                                                                                                               [00:00:47] backing up...                  ████████████████████████████████████████ 702.86 GiB/702.86 GiB 14.81 GiB/s  (ETA -)                                                                                                   
Files:       0 new, 46 changed, 95272 unchanged
Dirs:        0 new, 15 changed, 6365 unchanged
Added to the repo: 15.0 MiB (raw: 47.6 MiB)
processed 95318 files, 702.9 GiB
snapshot 4849242f successfully saved.

real    3m8,510s
user    0m17,463s
sys     0m9,024s