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List:       linux-ha-dev
Subject:    Re: [Linux-ha-dev] Hi list!!
From:       "Stephen C. Tweedie" <sct () redhat ! com>
Date:       1999-10-22 12:54:47
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Hi,

On Thu, 21 Oct 1999 20:05:33 +0000, Crispin Cowan <crispin@cse.ogi.edu>
said:

> I am very interested in process checkpoint and rollback.  ...

> I implemented a crude form of checkpoint and rollback for processes,
> but couldn't do anything about rolling back file state.  Can a
> journaling file system give me the hooks I need to be able to
> checkpoint and rollback the state of one or more files?

No.  The journal does not keep any form of snapshot other than a record
of the immediately outstanding IO pending on the filesystem.  It would
break the journal semantics completely to have any form of long-term
snapshot in the log.

Snapshots are still useful to have, but implementing them is an
orthogonal issue to journaling.

--Stephen

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