[plug] Backups

[Craig Ringer]

James Devenish wrote:
> In message <410606A1.2070906 at postnewspapers.com.au>
> on Tue, Jul 27, 2004 at 03:39:13PM +0800, Craig Ringer wrote:
> 
>>The time honoured approach is using an archiver like tar, pax, or cpio. 
> 
> Absolutely. One note about `dump` recovery (merely as an example to
> contrast against pax, tar, and cpio): it restores inodes, folder
> timestamps, driver nodes, ACLs, etc, which tar won't necessarily do.

If you're worried about ACLs you should probably be using star, which 
WILL restore them. IIRC recent pax versions will too. I don't know about 
folder timestamps, and I can't imagine any archiver being able to 
restore inode numbers without some serious low level filesystem magic 
and special support from the filesystem driver. Any decent archiver 
should be able to handle device nodes without fuss, though.

Another issue is that many of them don't restore hard links, and it's 
especially dificult to do so in incremental backups or backups of a 
subtree of the filesystem.

> But the obvious downside is that `dump` tools are filesystem-specific
> and the format is not particularly 'transparent and portable' in the
> same way as others.

Indeed. I've never been too sure about using filesystem dumpers, in part 
because of issues that they might be a wee bit /too/ faithful and 
possibly reproduce some forms of FS corruption. I'm also not sure how 
easy it is to do a partial restore, or to restore into a working 
directory or temporary volume. It doesn't help that I don't really know 
enough about them either.

I think I'd prefer to use a `dump` program, if availible for the 
filesystem type I was working on, in preference to `dd`, though.

--
Craig Ringer