[Fedora-livecd-list] Kadischi - preload utilities and daemon

[Jane Dogalt]

--- "J. Hartline" <jasperhartline at adelphia.net> wrote:

> Jane Dogalt wrote:
> 
> >Have you ever tried making 4 equal partitions on a hard disk (or just 2
> small
> >ones the same size on the outer and inner cylinders), and done hdparm -t
> tests
> >on them to check read speed?
> >  
> >
> I haven't but I just did on a HDD, makes no significant difference that 
> I can tell.

The difference probably lies in our definition of signifigance.  I routinely
see at least a 5% speedup between outer and inner cylinders.  On some random
disk with just 2 partitions, if you do repeated hdparm -t tests (to get a
consistent average), of the 2 partitions, you should notice, perhaps, a 27MB/s
to 28.5MB/S reading.

It's not mind crushingly fast, or even the low hanging fruit, but the read
speeds between the outer and inner cylinders are in fact different due to the
speed differential (more of the media surface area is passing under the read
head during the same amount of time, given a constant rpm)

> 
> >The speedup is signifigant, which makes me think it might work on cdroms as
> >well.  So if you can get all your files you want preloaded into cache to get
> >read in a single big chunk from outer cylinders, maybe...?
> >
> >But no, thats definately an optomization to worry about a long time from
> now.
> >  
> >
> Yeah. Overall I believe the transition to SquashFS for the rootfs would 
> be good for size definitely.
> On CD media alone probably speed too, though with DVD media I'm almost 
> positive it would be
> something outrageous. DVD reads are fast anyways.
> 
> Another thing I was seeing a few weeks ago was the optimized cloop 
> filesystem used on Librenix, I think it was.
> I've been told on some CDs made with Kadischi booting the CD sounds like 
> a bag of nails.
> Hah!

I think that must be the same thing as the accelerated knoppix (and "live cd
accelerator toolkit") from these guys-

http://www.alpha.co.jp/ac-knoppix/index_en.html

Basically profiling which files are accessed during a typical boot, and
reordering their physical location on the filesystem to reduce seek time.  I
wouldn't be surprised if they reordered them such that in addition to lying
together (physically close cylinders, such that seeking requires shorter
movement of read head), that they also put them towards the outter cylinders,
to gain that extra 5%.  

In addition to the cloop profiling, it sounds like they also tweak the dynamic
hardware autoconfiguration.  But I suspect that is a distribution specific
thing that fedora users will have to do in their own way.

-jdog


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