[ale] one or many...

[Jeff Hubbs]

On Fri, 2004-01-02 at 10:47, bo bo wrote:
> >Message: 5
> >From: Jeff Hubbs ...Date: 31 Dec 2003
> >
> ><snip>
> >I'm trying to make intolerably slow machines
> tolerable >and one of the ways I do that is by putting
> different >parts of the filesystem tree on different
> partitions / >drives....
> ><snip>
> 
> Jeff,
> 
> If I have only one drive, is there benefit from a
> specific partition order: ie., /boot; /; /usr; /var;
> /home; /tmp; - or something else? And is there a
> 'best' position for swap (only have one drive)?
> 
> thanks in advance,
> Bo

Bo -

So much of the answer would depend on what the machine is going to be
doing that it's hard to give you an answer.  

In past years, the first cylinders on a drive were significantly faster
than the outer last ones.  That being the case, it would have been wise
to put your most-used partitions toward the beginning, including swap
*if* it were expected that the machine would be hitting swap hard
routinely *and* the same drive would not also be doing significant
read/write at the same time.  In more recent years, this conventional
wisdom may have fallen by the wayside if only because disk drive
manufacturers may have abstractionalized the actual physical read/write
mapping to high degree.  You probably realize that the C/H/S count
reported by and printed on the drive has not been accurate for quite a
few years; that, I think, is when the abstraction began.  You can be
pretty sure that any drive that says it has 16 heads has nothing of the
sort and you probably have to look up a drive's specs online to find out
how many heads it really has (that *is* still an important number,
because a many-headed drive can work "across the platters" more than a
fewer-headed drive and that makes many-headed drives faster, at least to
a point - more heads means more arms and therefore more rotating mass
for the servo to try to sling back and forth).  

At this point in time, I have no reason to suspect that reported
cylinders are really physical cylinders.

Because of that. the best thing to do, given only one reasonably modern
drive, is to set up your machine however seems best and if you want to
go through the effort, try your typical operations with it set up vastly
differently and see if you can tell any difference, even if only
subjectively.  

If you really care about speed, it makes so much more difference to
break up operations among more than one drive and especially controller
and drive (to include hw/sw RAID) or use a filesystem that is
specifically stronger for your usage (e.g., Reiserfs for collections of
files 4K and less) that partition-order-on-single-drive issues just
don't matter much.  And, of course, if you REALLY REALLY care about
speed, you'd be using RAID as a matter of course and throwing entire
drives at the problem, therefore making within-drive partition issues
pretty much academic.

- Jeff