[Tfug] OT: Disk testing

[Bexley Hall]

Hi, Ronald,

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

> You may be right on most accounts, testing HD's is
> not the sort of thing I do,

Nor I!  :>  I design embedded systems -- hence the
inherent bias to look for *that* form of solution  :>
("when what you have is a hammer, everything looks
like a nail")

> I do get payed to develop test for power
> conversion products, but its not the same.

Yup.  I'd imagine you have to worry more about
environmental stresses, etc.

> In general I don't like to invent, its usually a
> wast of my time, and it always gets undone in a 
> few years when the setup has to go to Mexico or
> China.

Nor do I.  I *reuse* (I've been doing this sort of
thing for a fair number of years so I have LOTS of
already debugged designs -- software + hardware -- to
cull from).

> I like things with a well defined interface, 
> both hardware and software,

Hence the beauty of the IDE connector.  Or, at
the other end, the USB connector.

> I've even made up my own term "Modular 
> Components Off The Shelf". Its Maintained, invented
> and extended by 
> not-me, but it should be open if needed. If the ATA
> interface is simple, 
> thats all the more reason to use it. Adding layers
> like USB or Ethernet, 
> have caused me some problems with other data buses,
> and I have limited 
> kernel or driver software skills, although I have
> done a lot with 8 bit 
> MCU's without a proper OS. So the idea of an MCU
> sounds good, but 

Problem with a small/cheap MCU is tying that to
a host gets "expensive" (in terms of software
if you want any sort of bandwidth).

> basically that is what CORAID is doing with ATA over
> Ethernet, which would also seem elegant.
> 
> http://www.coraid.com/
> 
> The problem with the Coraid product is that it will
> not stand up to much 

It also looks to have a higher layer of abstraction
than is needed.  E.g., conceivably, you could
exchange commands with a "dumb" remote like:
"report drive geometry" (assume the remote adopts
that geometry unconditionally), "perform random
read/write/verify test", "scan surface", "scan
surface with pattern", "report results".

> abuse. If speed is not an issue, then I have no idea
> what "comprehensive 
> surface analysis" is, anyway USB is clean at least
> for wiring, however a 
> mobile rack type thing can help when you are dealing
> with a lot of parallel control lines.

But you don't have a lot of parallel control lines
in this configuration -- unless you run the IDE bus
up the back and add a set of buffers at each
drive (to isolte the drive during [un]plugging).

> The wiring mess is in an enclosed fixture and 
> the device under test is put in a carrier, then
> loaded into the fixture, 
> its a basic method used to test many products.

Yes, but that's a lot of effort into building
a fixture.  I'm looking for something "on the cheap"

> PC's do eat a lot of space, and thats a real 
> problem, As far as power, a PC is less wasteful 
> over all.

That assumes you do it with a *single* PC,
single monitor/keyboard, etc.  And, that the PC
only has what is needed -- no extra peripherals
that don't contribute to the task of checking
the disk.

If you start using multiple PC's -- and multiple
monitors, etc. -- then each new PC adds another
big chunk to the effective "quiescent power" :>

> Every power conversion device eats some bias power
> (2% or more) and smaller supply's are the most, 
> with high bias (~10%) and are less efficient.
> So a single PC supply (say 600W) running everything
> is about the most efficient method power wise. 

But that doesn't mean that you *still* can't use
a single supply to "power everything" -- even if it
is NOT in a PC!  E.g., you can still run pigtails
to each of the "external drives" from that single
supply (assuming you watch IR losses)

> Many PC's have a power supply that is a real POS
> and need replaced with a good one that includes
> PFC. The power supply will only use what is
> needed, plus its bias power, and efficiency factor.

The other downside to a single supply is that it is
larger (capacity) and thus overloads at a much
higher load (e.g., now you have to worry about
someone plugging/unplugging a 5VDC line that may
current limit at *50*A instead of 10).  And,
anything that goes wrong (e.g. someone failing
to switch power to the individual drive *off*
before unplugging/plugging and "misconnecting"
to the load -- or, two power pins touching
a piece of metal, etc.) now you put all of the
devices on that load at risk -- i.e. you have
to retest them all, reboot the PC, etc.

But, the single PC issue is still a bottleneck,
IMO.  IDE cables are supposed to be *short*.
So, you end up stuffing a lot of IDE cards into
a machine and then *hoping* you can fan those
out well enough to connect to N drives mounted
outside the PC, etc.  It just seems like a
cable dressing nightmare.

I think the quick-and-dirty solution would be to
find some very *small* PC motherboards with an
on-board NIC and IDE -- one or *two* ports.
Then, boot them diskless (eliminates the need
for a "master" disk on the primary IDE port)
and let each handle two drives -- one on primary,
the other on secondary IDE port.

The "PC" could be reasonably slow -- since all it has
to do is move bytes to/from the IDE.  And, you could
use the NIC to talk to the host (much easier than
using USB).

The key would be to find something very *small*
so that you could almost slip it under the UUT
without taking up much space, etc.  If everything
is on the motherboard, then it could be a low
profile since no ISA/PCI cards sticking up...


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