Re: [PATCH] xfsdump: use the full 32-bit generation number

[Bill Kendall <wkendall@sgi.com>]

Christoph Hellwig wrote:
> On Fri, Jan 06, 2012 at 02:09:25PM -0600, Bill Kendall wrote:
>> dump format version has been bumped to 3. xfsdump also required changes to
>> its inode-to-generation cache. This map is not persistent though, so no
>> compatibility or version changes were required there.
> 
> Shouldn't the be an option to still generate the old format for
> compatibility reasons?

The new format contains more information than the old. The new
xfsrestore can drop back to using 12-bit generation numbers even
if the dump used 32 bits. It will do this automatically when
applying a series of restores if the oldest dump used only 12 bits.

It's possible that a site would revert to an old xfsdump in the
middle of a series of incremental backups, allowing for the oldest
backup to use 32-bit generation numbers and a newer backup to use
only 12 bits. xfsrestore won't get this right, so a case could be
made for having a "force 12-bit generation numbers" option on
xfsrestore.

You were referring to an xfsdump option. What use case did you
have in mind? Compatibility with an old restore?

Thanks,
Bill

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