[NTLUG:Discuss] Practice with clustering at home?

[Bryan J. Smith]

Thomas Cameron <thomas.cameron at camerontech.com> wrote:
> I heard during a Red Hat class I took that you could use
> firewire drives

Danger!  Danger!  Warning Will Robinson!  ;->

> to run Red Hat Cluster Suite in lieu of buying a SAN.  I
> have never used firewire, being more of a USB kind of guy.

USB was never designed to compete with FireWire, it was
designed to complement it at the low-end.  E.g., DeviceBay
and other standards.

USB was never designed for high-speed block devices, and
cannot do device-to-device transfers -- let alone its
virtually impossible to get more than a few devices on the
same bus because of inter-device fighting.  This was due to
the fact that Intel-Microsoft designed USB controllers and
host drivers rather simplistically, putting all the "brains"
(and vendor-defined standards) at the end-device.  That's why
it took about 3-4 years after OHCI controllers were on
mainboard before the devices came out.

These things are unheard of in FireWire, where it was
designed for multiple targets off-the-bat.  The only reason
USB is more popular is because Intel changed its mind on
licensing FireWire.  When the FireWire logic was thrown out
of the PIIX southbridges, that was it, 90% of consumers were
cut off.  Especially considering that FireWire is not
expensive at all (which renders the whole BetaMax v. VHS
comparison moot).

Another common assumption is that USB 2.0 is 480Mbps.  Not
only can Intel get no where near that (and have admitted the
limitations), you have to have an EHCI controller to get it. 
All but 1 controller on a supposed USB 2.0 IC is typical OHCI
and only capable of 12Mbps.  On FireWire, nothing is capable
of less than 100Mbps, and 400Mbps is the norm.

> Anyone have any idea how to make a single firewire disk
> available to multiple servers, kind of like a SAN?

Yes, and I highly recommend _against_ it.

I would investigate going with Serial Attached SCSI (SAS)
instead.  Much more stable and designed explicitly for it. 
FireWire is fine as a narrow SCSI external device
replacement, but there's a lot missing as a full SCSI
replacement.

Sadly enough, USB is really more akin to age-old EIDE with
programmed I/O (PIO), only worse.  There were at least a
half-dozen _better_ serial protocols that had been around 10
years, but USB got the call because it was ultra-simplistic
for Intel and Microsoft to claim they were shipping it
(again, even though devices .  Anyone who has written a block
driver for a USB device knows what I'm talking about.  ;->

For more on SAS, see my blog: 
http://thebs413.blogspot.com/2005/08/serial-storage-is-future.html
 

The SAS concentrators shouldn't be too terribly expensive.


-- 
Bryan J. Smith                | Sent from Yahoo Mail
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