Date: 5 Feb 1999 14:12:59 +1100 From: "John Saunders" <john.saunders@nlc.net.au> To: freebsd-stable@FreeBSD.ORG Subject: Re: dump -> multiple fs'es and computers Message-ID: <19990205031259.11648.qmail@nhj.nlc.net.au> In-Reply-To: <19990204200506.E299C45859@pobox.com>
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Jon Hamilton you 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. Benefit of incremental is that the amount of data backed up is on average the same for each incremental. Bad side is that a recovery requires the last full back + _all_ incrementals to be restored. Benefit of differential is that a recovery only requires the last full backup + the last differential to be restored. Bad side is that the amount of data stored to the differential grows each day. P.S. You can also do simple network backups using rsh to run dump on another machine and using <host>:/dev/nrst0 as the tape name. e.g. dump ... tapehost:/dev/nrst0 / dump ... tapehost:/dev/nrst0 /usr dump ... tapehost:/dev/nrst0 /var rsh otherhost dump ... tapehost:/dev/nrst0 / rsh otherhost dump ... tapehost:/dev/nrst0 /usr rsh otherhost dump ... tapehost:/dev/nrst0 /var rsh andotherhost dump ... tapehost:/dev/nrst0 / rsh andotherhost dump ... tapehost:/dev/nrst0 /usr rsh andotherhost dump ... tapehost:/dev/nrst0 /var P.S. Keep a hard copy print out of your backup script (and disk partition/labels). That way if bad juju strikes you know how to repartition the new drives and what each dump file on tape is from. I missed out on the partition info, result was it took time to work out how big to make each partition again on the new disk. And when the phone is ringing non-stop it's hard to think clearly :-) Cheers. -- +------------------------------------------------------------+ . | John Saunders - mailto:john@nlc.net.au (EMail) | ,--_|\ | - http://www.nlc.net.au/ (WWW) | / Oz \ | - 02-9489-4932 or 041-822-3814 (Phone) | \_,--\_/ | NHJ NORTHLINK COMMUNICATIONS - Supplying a professional, | v | and above all friendly, internet connection service. | +------------------------------------------------------------+ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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