Date: Thu, 4 Feb 1999 21:41:46 -0800 (PST) From: Mike Meyer <mwm@phone.net> To: freebsd-stable@FreeBSD.ORG Subject: Re: dump -> multiple fs'es and computers Message-ID: <Pine.BSF.4.05.9902042119430.8187-100000@guru.phone.net> In-Reply-To: <19990205031259.11648.qmail@nhj.nlc.net.au>
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On 5 Feb 1999, John Saunders wrote: > > There's a tutorial on using dump for backups on my web site at > > http://www.pobox.com/~hamilton/dump.html which may be of some use as well. > > One thing that all the dump man pages/tutorials never fully explain is > the significance of dump levels. They sort of explain what they do, but > never fully explain how to apply these to making full/incremental/ > differential backups. Basically: > > Full backup means use dump level 0, period. > > Incremental (backup changes since last backup of any type) means use > ascending dump levels other than 0. i.e. Do a full backup Friday night > with level 0, then use levels 1 2 3 4 5 6 for Sat through Thu. > > Differential (backup changes since last _full_ backup) means use > descending dump levels other than 0. i.e. Do a full backup Friday night > with level 0, then use levels 6 5 4 3 2 1 for Sat through Thu. Or > simply use the same level for each night. I prefer a different level > so that /etc/dumpdates has a weekly history. I suppose that terminology is correct from somewhere, but the dump man page says "incremental" is dump except a level 0. I.e. - anything that only dumps incremental changes since some prior dump. To be precise about what dump does, a level N dump saves all new files since the last dump at a level lower than N, or everything on the disk if there is no such dump. Since there are no dumps lower than level 0, they always dump everything on the disk. (bonus question - why is this type of backup system impossible on an MS-DOS system?) Given that, there are any number of possibilities between the two extremes mentioned above, including the tower of hanoi mentioned on the man page. Some of the ones i've seen include a school, that did Level 0's after every semester (before you delete the students semester accounts). Level 5's at every Saturday except the first saturday of the month, which is level 3. Level 9's every day - to a dedicated file system, which is tar'ed off to tape when you're through. On systems with lots of activity, we did level 7's on Wednesdays. Normal restore is two (or, for very busy systems, three) tape backups plus the latest incremental from disk. One corporate client required complete backups of all work to be sent to the corporate storage site every month. So we did level 3's on saturdays, except the first of the month was level 0s. Then 7's every other day of the week (again, to disk). Personally, I run level 0s to CD-ROM, level 5's on Saturdays, and level 8s every day. If I do a major change on a system, I'll do an intermediate level so I don't wind up dumping the new stuff every day/week from then on out. If I'm going to do something that seems a bit risky, I'll take a level 9 of the file systems in question before preceeding. Incrementals go to a Jazz cartridge. When it fills up, I delete all the dailies that aren't current, but keep the weeklies for archival purposes. When what's left over after that starts looking like a CD-ROM's worth of stuff, I press one from it and delete everything on the JAZZ disk except the last set of dailies. <mike To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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