Understanding pruning

[Droolio]

is it necessary to have
-keep 1:1
in keep options ?

Nope, not necessary - if you only do daily backups.

Only this
-keep 7:90
not means this ?:
Keep 1 snapshot every 1 day(s) if not older than 90 day(s)
Keep 1 snapshot every 7 day(s) if older than 90 day(s)

Strictly speaking, only -keep 7:90 means:

Keep 1 snapshot every 7 day(s) if older than 90 day(s)

With no other -keeps, anything less than 90 days won’t get pruned at all. So IF you did hourly backups, you’d have 90 x 24 backups within that age range. Otherwise, daily backups would leave the last 90 backups plus the weeklies beyond 90 days.

[Arty.R]

Thanks guys, I seem to understand how it works)
final question from me ))

this structure means
-keep 0:1800 -keep 90:730 -keep 30:365 -keep 7:180 -keep 3:90 -a

Keep 1 snapshot every 3 day(s) if older than 90 day(s)
Keep 1 snapshot every 7 day(s) if older than 180 day(s)
Keep 1 snapshot every 30 day(s) if older than 365 day(s)
Keep 1 snapshot every 730 day(s) if older than 730 day(s)
Keep no snapshot if older than 1800 day(s)

Right ?

[Droolio]

Close. That outcome looks almost like the output you get when running prune… if you want to see exactly what it does without actually performing it, just add -dry-run to the command:

$ duplicacy prune -a -keep 0:1800 -keep 90:730 -keep 30:365 -keep 7:180 -keep 3:90 -dry-run

Keep no snapshots older than 1800 days
Keep 1 snapshot every 90 day(s) if older than 730 day(s)
Keep 1 snapshot every 30 day(s) if older than 365 day(s)
Keep 1 snapshot every 7 day(s) if older than 180 day(s)
Keep 1 snapshot every 3 day(s) if older than 90 day(s)

[Christoph]

CrashPlan had this option where you could tell it ‘never remove deleted files’ which I guess meant old revisions would get pruned but there’d be at least one copy.

See also this topic:

Prune options for handling of deleted files

But it could be done? How about something like this: Before deleting a fossil, duplicacy checks whether the filename to which the fossil belonged still exists in any snapshot, if it does, it deletes it, if not, it gathers all the other chunks that belong to that file and adds them to a kind of virtual snapshot in which it references all the deleted files. Perhaps this could be snapshot 0 in each snapshot ID.