Rasmus Andersen wrote:
If you do backup live filesystems/data then dump is on par with dd; both read from the underlying device and might bypass the kernel's page cache. Ie., there might be unwritten data cached thats not on disk yet. Tar/rdiff-backup/etc reads through the pagecache and avoids this problem. The dump people talk a bit about this themselves on http://dump.sourceforge.net/isdumpdeprecated.html Note I dont want to dis dump, backing up live filesystems is just tricky (depending on your consistency requirements :) and dump adds another level to that.
Understood - I have seen that article too. I must say, I've mainly had experience with 'dump' on Freebsd and 'xfsdump' on Linux, and never had restore issues with *either* of these. Now I'm not sure whether these are supposed to be better than 'dump' on Linux aimed at ext2|3 filesystems - certainly Freebsd's 'dump' has an option to tell it that it is dumping a 'live' filesystem, and the man pages for xfsrestore have notes concerning what happens when restoring an (xfs)dump from a 'live' filesystem - so they may well be!
On the other hand I've certainly routinely seen cases of people using dd (rsync, cpio, tar etc) and coming to grief at restore time. I am reluctant to suggest that folks use xfs and hence get access to xfsdump, as one of the nice things about Linux is the choice of a variety of filesystems - but it is pretty important to get able to backup of (for instance ) / ... and you usually don't have much option other than doing it live!
regards Mark -- gentoo-user@lists.gentoo.org mailing list
