Date: Fri, 8 Mar 2002 18:30:39 -0600 From: "Mike Meyer" <mwm-dated-1016065839.1ce4c2@mired.org> To: Jon Wilson <jon@netcraft.com> Cc: questions@FreeBSD.ORG Subject: Re: questions about dump on live filesystems Message-ID: <15497.22447.463355.749616@guru.mired.org> In-Reply-To: <20020308091152.X74454-100000@beta.netcraft.com> References: <15496.5730.638025.424864@guru.mired.org> <20020308091152.X74454-100000@beta.netcraft.com>
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Jon Wilson <jon@netcraft.com> types: > On Thu, 7 Mar 2002, Mike Meyer wrote: > > > 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. > Not very well! (rusty C, laziness, etc!) Ok, I checked the code. > > It sure sounds like that's what will happen. > Y. But level 0's are *special*. Not that special, though - the time of the "dump" is the time the dump started for all levels; any files changed after that will be dumped at the next dump of one greater level. > I admint that it's odd, but I don't see how it causes any major problems. > The amount of data we are talking about is large, and on a high use > system, so level-0 single-user takes some time. Minimising user disruption > is a priority. So make them *rare*. Basically, do level 0's in single user mode. Do a level 3 at the beginning of each month, a level 6 each week, and a level 8 every day. Then only do another level 0 when the level 3 starts taking "to long" in multiuser mode. Wouldn't you rather have one full dump of downtime a year than short partial dump downtimes every day, and know that you've got a good full dump to work with? Either that, or convince someone this is a critical resource, and spring for a RAID mirror of the user data. > > 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. > I'm not following you here. According to my understanding, a level-($n+1) > backup will include all files changed since the last level-$n. What is the > point in incrementing by more than one in this way? If you do a level n and then level n+1, there's nothing you can do if the elvel n+1's suddenly triple in size except doing a new level n. By spreading them out a bit, so that you do level n's and then level n+3's, if that happens you can do a level n+2 to pick up the bulge, without having to do a full level n. Similarly, my dailies are always at level 8. So when I upgrade a system, I do a quick level 9 after shutting it down to single user, just in case. That gives me the safety net of a full backup, but at the cost of just backing up the few things that have changed that day. <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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