[NTLUG:Discuss] RE: Practice with clustering at home?

[Bryan J. Smith]

Burton Strauss <Burton_Strauss at comcast.net> wrote:
> Danger Leaping Lemurs: Bryan, you saw the letters U S and B
> and jumped to the wrong conclusion.  And started off
> flogging deceased equines per usual.
> What Thomas was really asking is for information on using
> FireWire for a low-end cluster. 

I'm going to respond to this a second time.

First off,  I did _not_ miss it at all.  From that same post:
 

   "TC>>> you could use firewire drives
    Danger!  Danger!  Warning Will Robinson!  ;->"

    TC>>> 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.

    ...
    
    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."

And secondly, yes, I talked a bit on USB.

To come back to it, I guess I should have done a _full_post_
on "multi-device targetting" -- which USB doesn't do -- and
"multi-host targetting" -- which FireWire really doesn't do
-- but _is_ required for "storage failover."  But then you'd
just complain about me giving a theory on storage when it's
not necessary either.

In a nutshell, when someone starts saying things like "I've
only used USB" in the context of FireWire as a storage
failover, then there's a lot of concepts that haven't been
covered.

Again, USB is one device, one channel, devices on the same
channel cannot talk to each other (if they don't already
conflict -- especially for block devices).  No multi-device
targetting, no multi-host targetting.

FireWire is multiple devices per channel.  Multi-device
targetting, but no multi-host targetting.  The problem is
that some people deploy FireWire and have multi-host
targetting, typically with data loss.

iSCSI attempted to introduce low-cost SAN, but it's got a lot
of overhead -- at both the target and host.

SAS is going to do a much better job, at much higher speed,
with less overhead, and the only negative being cable length.


So again, next time, I'll just write a blog entry and point
to it instead of trying to address so many missing concepts
in a couple of e-mails.


-- 
Bryan J. Smith                | Sent from Yahoo Mail
mailto:b.j.smith at ieee.org     |  (please excuse any
http://thebs413.blogspot.com/ |   missing headers)