repair.strip and backups

[timeless]

On Wed, Aug 11, 2010 at 6:06 AM, Nicolas Dumazet <nicdumz at gmail.com> wrote:

wrt strip artifacts, i sometimes need one of the bundles, and on rare
occasions i think i want the one that went away. i know there was a
time when i used to get both. but i can't remember what i was doing
when i wanted this stuff, so that's not the point of this message.

> == Compression ==
>
> repair._bundle uses by default BZ2 compression.
> For "full bundles", it makes sense, as those are likely to be kept
> around. But partial bundles are temporary, merely an internal detail.
> Compressing takes time when bundling, and needs time when unbundling.
>
> I think that in ALL and NONE cases, where temp bundles are not kept, we
> could get rid of compression, speeding up the related commands.
> I have a patch doing this. Any comments?

Sometimes compression is actually cheaper than disk i/o.

This is going to depend on the individual file system (we can call
this a repository i guess). But it will typically be fixed for a given
user or install.

Bad example:

wam.umd.edu is part of /afs/umd.edu/

on an average box there, you had:

/tmp <ram disk = very fast> ~4gb
~ <afs = slow> ~25mb (in 1998)

the computer itself was "fast", so compression for ~ made sense
because reading/writing over the wire to reach ~ was more expensive
than the cost for compression. for /tmp, compression mostly didn't
make sense except to the extent that space used by /tmp competed w/
space for other applications.

This is essentially an argument for an hgrc setting to control compression.