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Re: Reality of delta benefit

From: Zack Weinberg <zack_at_wolery.cumb.org>
Date: 2000-08-17 18:32:51 CEST

On Wed, Aug 16, 2000 at 05:47:39PM -0400, Jonathan S. Shapiro wrote:
> In case this is useful to the delta storage debate...
>
> The other day, in the process of figuring out how big a farm to buy, I ran a
> size analysis on the EROS source repository. Basically, I expanded every
> version ever and examined the disk consumption in blocks under various
> compression schemes: RCS, gzip, bzip2, etc.
>
> Somewhat to my surprise, RCS is only very slightly better than gzip (normal
> compression -- nothing fancy) on this data set and roughly the same as
> bzip2.
>
> Is this comparable to other measurements people have seen? If so, it strikes
> me that storing deltas in the repository itself may multiply I/O's and file
> operations for very little benefit.

Did you try compressing the ,v files? It seems likely that delta
encoding and then general compression would do better than compressing
each version individually.

At the risk of broken-record-ness, the SCCS weave format is
consistently smaller than RCS format for the same set of versions, and
takes the same time to extract any revision.

zw
Received on Sat Oct 21 14:36:07 2006

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