Date: Thu, 7 Mar 2002 19:39:46 -0600 From: "Mike Meyer" <mwm-dated-1015983587.a34c38@mired.org> To: Jon Wilson <jon@netcraft.com> Cc: questions@freebsd.org Subject: Re: questions about dump on live filesystems Message-ID: <15496.5730.638025.424864@guru.mired.org> In-Reply-To: <35854433@toto.iv>
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Jon Wilson <jon@netcraft.com> types: > Hi folks, > Looking at the code for dump, it appears to notice if an inode is changed > from being a directory to a file, or vice-versa, and does not backup data > from that inode. > > My question: what happens if an inode is freed and assigned to a different > file during the dump process? Will I end up with an erroneous bit of data > in my restored file? I haven't checked the code, you have. It sure sounds like that's what will happen. > Or can I at least rely on dump to leave things in a state such that (for > instance) I will get a valid backup of the file at the next level-$n++ > dump? A backup strategy of level-0 multi-user r/w, followed by a level-1 > r/o is what I would like to be doing, but various people here have doubts > about this producing valid backups 100% of the time. I think you've got those backwards. What I recommend is that you do the level 0 r/o, or in single use mode. The level 1 is then done multi-user and r/w. That way, even if the level 1 is screwed up, the next level 1 will cause try and back the file up again, as it will have changed since the dump started, which is what the next dump will be looking for. At least, that's the way I read the code. The thing to watch for is if the level 1 dump is done at the same time as some critical file being updated on a daily basis. That means that those files will be bad on every single daily dump, which is probably not acceptable. Actually, I recommend that you not do the level above level 0 as level 1, but as at least level 2. The exact level will depend on your system. Personally, I do level 0, 4, and 8, with 8's happening daily and 4's weekly. <mike -- Mike Meyer <mwm@mired.org> http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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