Hello Radosław, Am 07-Sep-2021 10:38:44 +0200 schrieb rados...@korzeniewski.net: > pon., 6 wrz 2021 o 20:21 <neumei...@mail.de> napisał(a): > > But I'm quiet sure that I do understand the behaviors of them. However In > > case I did get something wrong I will write out > > the behaviors and would acknowledge if someone could point out if I should > > got something wrong. Thank you. > > > > For a given job: > > -an incremental backup references the most recent backup of any > > kind(incremental,differential,full) and backups all the data that changed > > since then > > -a differential backup references the most recent differential or full > > backup and backups all the data that changed since then > > No, any differential backup refers to the recent full backup only. So it > backup all changes from full and basically every subsequent differential > backup "includes" all changes available in previous differential backups. > The idea behind differential levels is that you need a single differential in > the restore chain to optimize the restore procedure.
That's right, I got that wrong. Thank you. Phil pointed that out too. > > -a full backup references nothing and backups all the data > > > > You have got me right. You wrote: "If you are doing a "daily" and a > > "weekly" incremental of the same job, > > then the "weekly" either isn't really "weekly" or isn't really incremental." > > That's exactly what I was attempting to do. My goal was to shrink the space > > all my backups need by introducing a second > > incremental-pool with a longer retention period, but this leads straight to > > the problem you have described under the > > "Now what you COULD do, ..."-paragraph that I am trying to avoid. I'm Sorry > > that I didn't made it clearer. > > Thank you for pointing out the Virtual Full option. I didn't know about > > that. > > Differential backups are not designed to optimize for "space". They are > designed to optimize restore procedures. > > Just take a look for an example backup levels policy: > - Full once a month > - Differential once a week > - Incremental every day > > In this case if you need to restore the whole month of data from backup then > you will need a single Full + a single (third) Diff and a few (up to six) > Incrementals. > On the other hand the "standard" Full + every day incrementals without > intermediate diffs requires a single Full + about 30 Incrementals. Ah I see, that makes sense. I think by introducing the differential-backups there comes a slight spacesaving-effect with it, since someone doesn't need to keep the incrementals around for that long. Right? But I understand that this was not the main goal why it was developed in the first place. > > There just popped up another question in my head: > > - should I preferably use the Virtual Full option to make full backups or > > the normal full backup-option? Are there any downsides? > > The virtual full option is the right solution in most cases if you have > resources to implement it. For example it requires no less than 2 archive > devices defined in Storage Daemon, so if you have a single tape drive it > simply won't work. Okay I will look deeper into it this evening with a little bit more time and will come back if I should have any questions left. Thank you. Sebastian ------------------------------------------------------------------------------------------------- FreeMail powered by mail.de - MEHR SICHERHEIT, SERIOSITÄT UND KOMFORT _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
