Speeding up live cd boot through optimizing file layout

[Matt Zimmerman]

On Mon, May 29, 2006 at 04:25:18PM -0700, plougher wrote:
> 
> Matt Zimmerman wrote:
> >Optimizations like this are rarely so simple, and certainly not in this
> >case.  The advantage of the outer edges is in throughput, not latency.
> >Placing a file there, away from most other files, requires that the drive
> >seek a long way to get at it.  Meanwhile, caching means that files which
> are
> >accessed very frequently will be held in memory anyway, so this could even
> >be a net loss in performance. 
> 
> By and large this is correct.  However, there are a couple of reasons why
> moving files accessed together at start-up to the edge of the disk works
> well on Squashfs.

The above was written in response to a proposal to move the single most
frequently accessed file to the edge of the disk; what you are describing is
something quite different: grouping the files read at boot in one place on
the disc.

This, in fact, has a reasonable chance of improving performance, since all
of these files are read in a single pass by /etc/init.d/readahead.

-- 
 - mdz