Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!cis.ohio-state.edu!pacific.mps.ohio-state.edu!verber From: verber@pacific.mps.ohio-state.edu (Mark Verber) Newsgroups: comp.unix.admin Subject: Re: SUMMARY: Backup while in multi-user mode Message-ID: Date: 22 May 91 15:23:56 GMT References: <1991May20.204327.17694@erg.sri.com> <690@silence.princeton.nj.us> <43617@netnews.upenn.edu> Sender: news@pacific.mps.ohio-state.edu Organization: Ohio State University; Physics Department Lines: 41 In-reply-to: rsk@gynko.circ.upenn.edu's message of 22 May 91 13:16:09 GMT In article <43617@netnews.upenn.edu> rsk@gynko.circ.upenn.edu (Rich Kulawiec) writes in responce to my question about doing level 0 dumps in single user mode using BSD 4.3 dump+purdue+brl hacks which are less likely to have problems with active file system: Those mods aren't bulletproof -- but in about five years of using this version of dump on many machines (VAX, Sun-3, Sun-4, MIPS, Pmax, etc.) I've never encountered a dump that I couldn't restore, i.e. that wasn't self-consistent. That doesn't mean that all such dumps were "complete", especially since the meaning of "complete" gets fuzzy when we attempt to apply that term to an active filesystem; but it does mean that I had what I needed to recover from crashes. I am glad for you. On the other hand I have seen restored fail utterly when the dump was taken on an active file system. The dump we used has all the above patches installed! We all know even with all those mods that there are failure conditions: Chris Torek and others have posted them time to time so I am not going to repeat them. Murphy's Law indicates that when you are in critical need of a clean dump... that is when you happened to get an inconsistent one. I haven't found a corrupted dump tape often, but it has happened ... which is enough to keep me doing level 0 in single-user. I value my user's data. [This may come from an incredible three day period of time when the staff retyped an entire thesis for a graduating PhD candidate who lost everything after a series of failures.] Another thing to note is most of us are seeing more and more disk hanging off our machines. There are more files and more dumps being done. A few years ago most of us had 1-2gb of disk. These days sites with 5-10x that are common. That increases the total number of possible failures because a lot more dumps are being running. The sites I know who have seen inconsistent dumps are also sites that have 10-30 servers and 15-30gb of disk a few years ago. Mark Verber Ohio State Physics Dept / Computing Services