Re: Why daily and weekly?

[On 07 Mar, @ 23:51, Jeroen wrote in "Re: [hdup-user] Why daily and  ..."]
> >there are only 3 archives used to recreate an image, namely the last
> >monthly, weekly and daily. 
> 
> I understand. I talked to someone who uses rsync today. That's why I got 
> confused.
> 
> I also think I understand how hdup works and why it's not useful to 
> perform "hdup weekly" on a daily basis:
> hdup uses GNU tar's functionality to compare files' last-modified dates.

well, hdup actually uses the listed-incremental stuff, which is more
advanced then just checking the last-modification dates. Especially
when subdirectories are removed from disk. 

> "hdup weekly" uses tar to get all files modified exactly 7 days since 
> the last weekly diff. So if you ran "hdup weekly" every day you'd end up 
> with 7 identical backups every week since files that are <=6 days old 
> aren't included in weekly diffs.
> 
> Is this correct?

almost, the weekly's are "compared" with the last monthly. So if there
is change between week1 and week2 the backups differ. To sum it all
up:

monthly - null dump
     weekly 1       - all files changed since last monthly
         daily 1      - all files changed since last weekly 1
         daily 2      - all files changed since last weekly 1
	     ....      ...
         daily 7      - all files changed since last weekly 1
     weekly 2       - all files changed since last monthly
         daily 1      - all files changed since last weekly 2
     weekly 3       - all files changed since last monthly
     weekly 4       - all files changed since last monthly

> >per day - that way you only loose several hours worth of work, if
> >something bad happens. 
> 
> hdup can't do this because it "only" works with dates, not with date and 
> time?

yes. allthough changing the backup alg to allow this, is fairly easy,
but every time I start thinking about the restores it gets complicated.
(But I really haven't given this much thought)

--
grtz,
  - Miek

http://www.miek.nl                   http://www.nlnetlabs.nl