Re: Building Big Ass Linux Machine, what are the limits?

Stephen C. Tweedie (sct@redhat.com)
Thu, 1 Oct 1998 14:35:03 +0100


Hi,

On Wed, 30 Sep 1998 12:16:59 +0100 (BST), Redvers Davies
<kernel@madhouse.org.uk> said:

> Another feature that we can perhaps learn from this excellent company
> is the "snapshot" function.

> Obviously this is completely impractical for some applications (EG: news,
> mailservers etc) - But, in principle, would it be feasable to add this
> functionality into the journalling filesystem ?

No, not at all. Snapshotting is completely alien to the way ext2fs is
designed. Adding a journal to ext2fs won't change that. Adding
snapshots to a tree-based filesystem like reiserfs would be much
easier.

There are other options, however. It would be much easier to support
file versioning (keeping older versions of superceded or deleted files)
than to support snapshots, and true snapshots can be implemented at the
block-device level rather than in the filesystem. True ext2fs-level
snapshots won't happen, though.

--Stephen

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