[Tfug] OT: Disk testing

[Bexley Hall]

Hi, Ronald,

--- Ronald Sutherland <rsutherland at epccs.com> wrote:

> I'm thinking that USB will not scale past a few
HD's,

Yes, but adding more PC's uses up more bench space,
power, etc.  It's just not a very elegant solution  :<
And, one could always add more USB i/f's until you
max out the PCI bus.

(The "ideal" solution is a small microcontroller
attached to each drive to just push bytes in/out
that one drive and report results to a host that
presents the user interface -- but, I don't want
to have to layout a board for this...)

> I guess I'd personally be thinking along the 
> lines of multiple PC's. With a test 
> program that runs after startup in each. I'd

Yes, if you ignore the cost of space and the
wasted power running a whole pc instead of
*just* a disk drive...  :<

> probably also get some 
> cheep IDE cards to add IDE channels, I've seen some
> that add 2 (or 4) 
> IDE channels from HighPoint and others, and if I
> remember they claim to work in Linux.

An IDE card is little more than a 16 bit buffer
and a connector.  Making one work in any OS is
a cakewalk.  :>

> After adding 4 IDE channels, one
> master drive per 
> channel, that should give 6 master IDE's total, keep

But now you have 5 disk drives dangling on 16"
ribbon cables sprawled on a desktop.  I have a hard
enough time getting two disks to dress nicely in a
single case -- let alone one inside and 5 outside!
(you don't want to ount the drives inside unless you
can do so without fasteners... which means you
now have to look for a case that will accommodate
this, etc.)

> one for system and 
> use the rest for testing. Since I've never tried
> this sort of thing, I 
> wonder if its possible to kill the power to an IDE
> master only and 
> remove it while leaving the other masters running.

You can do this -- assuming no slave attached.
But, it is not "good form".  You are just waiting
for something to die, somewhere.  Putting a
mechanical switch (DPST) in line with the power
connection can help.  I just feel it is easier to
power off an external USB drive enclosure (which
is already *expecting* to be used in this fashion)
and then unplugging the cables.

> Also I think that the 
> PCI data bus will saturate around 5 to 6 HD's so
> more than that per 
> system may not be faster, if I'm wrong about that
> then fill more PCI slots with IDE cards.

It depends on how you are exercising the drives
and the characteristics of the drives.  E.g., if
you deliberately do random seeks, then you invalidate
any internal cache benefits for the drives and are
limited by access times, not bandwidth.

Also, I think some newer drives can be told to
format themselves thereby cutting down on bus
usage, etc.

(sigh)  It may prove easier to just hack together
a small microcontroller and stuff one on each
drive.  This would eliminate all of the cabling
issues, bus bandwidth limitations, power supply,
etc.  I'll have to see what I can find for a single
chip solution as that might let me get away with
a little 2"x2" PCB -- perhaps just plug it
right onto the back of the drive!  :>

Thanks!
--don

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