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Subject: Re: ext4 features
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Bill Davidsen <davidsen@tmr.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>, Theodore Tso <tytso@mit.edu>,
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Date: Thu, 06 Jul 2006 08:43:15 -0400
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On Wed, 2006-07-05 at 22:32 -0400, Bill Davidsen wrote:

> But with timestamps I need remember only one number, the time of my last 
> backup. Skipping over the question of "who's idea of time" inherent in 
> network filesystems. I compare all ctimes with the time of the last 
> backup and do incremental on the newer ones. If we use versioning I have 
> to remember the version for each file! In practice I really question if 
> the benefit justified keeping all that metadata between backups. And if 
> I delete a file and create another by the same name, what is it's version?

You are completely missing the point. Our background is that all NFS
clients are required to use the mtime and ctime timestamps in order to
figure out if their cached data is valid. They need to do this extremely
frequently (in fact, every time you open() the file).

Nobody gives a rats arse about backups: those are infrequent and
can/should use more sophisticated techniques such as checksumming.

Cheers,
  Trond