Date: Thu, 7 Mar 2002 11:19:49 +0000 (GMT) From: Jon Wilson <jon@netcraft.com> To: <freebsd-questions@FreeBSD.ORG> Subject: questions about dump on live filesystems Message-ID: <Pine.LNX.4.33.0203071109350.32087-100000@ducky.netcraft.com>
next in thread | raw e-mail | index | archive | help
Hi folks, Here is a question regarding the integrity of backups made using dump on live filesystems (i.e. mounted read-write, machine in multi-user state). dump does 4 passes: scanning of inodes for directories and files, archiving of data in those inodes for both directories and files. So between the scan and the actual transfer of data to (e.g.) tape, there is a dely, which in a live system the inode could be freed and reused by another file. 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? 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. Please note that I am a sysadmin and application code developer, with only basic C knowledge, and not a OS developer, so I may need pointing in the right direction of the relevant file-system code and/or docs. Thanks, Jon -- Jon Wilson Netcraft Ltd. Tel: +44 (0)1225 867975 jon@netcraft.com Fax: +44 (0)1225 867700 http://www.netcraft.com Mob: +44 (0)7776 137939 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.LNX.4.33.0203071109350.32087-100000>