Need some help with my backup idea.
Jelle de Jong
jelledejong at powercraft.nl
Thu Sep 28 15:39:23 UTC 2006
Thanks for the information,
Dave Dodge wrote:
> I don't really have any answers, just comments:
> On Sun, Sep 24, 2006 at 04:32:18PM +0200, Jelle de Jong wrote:
>> Output must result in a one file image that can be mounted and read with
>> the mount tool. (like a dd image)
> This requirement complicates things, because it means the kernel has
> to be able to read your backup format. Using an existing filesystem
> format may not solve your problems because they're unlikely to have
> the space efficiency that you're after. Your best solution here might
> be a custom format with a custom FUSE backend.
>> All file stored in the image must come out like they came in (not like
>> some standard iso image)
> I'll complicate this further by adding some special cases that can be
> - Large sparse files. Many Unix-style filesystems will allow you to
> create files that appear to be many times larger than all
> available disk space. I used to have 1.44M floppy disks with
> 30-40 gigabytes of files on each of them. If you try to copy
> these by opening and reading them you have to be careful to not
> converting the missing blocks from the original into real blocks
> in the copy; otherwise you end up using more disk space or even
> running out entirely.
> - Files with multiple hard links. Ideally your backup and restore
> procedure should preserve the links.
> - If you back up on one machine and restore on another, what happens
> when the UID and GID values don't match on the two machines? Do
> you need to record the user and group names rather than (or in
> addition to) the UID/GID values?
> - Extended attributes. These become important in situations such as
> using SELinux.
>> But this will not cover the split an join function.
> Unionfs might help with that.
> -Dave Dodge
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