[G4] Firewire problem

[Perry The Cynic]

Here's what's going on: A and B are connected via FireWire. *You* think 
you're just doing this for networking, but the computers don't know that. 
They combine their FireWire buses into one "super-bus", which now contains 
A+B+the drive. (That's how FireWire works.) This means that, technically 
speaking, the drive is attached to *both* A and B, and whichever finds the 
drive first treats it as a local drive. Normally that's A (it's closer), 
but if you turn off A for wee bit, the drive will detach from A, and then B 
may find it before A gets back up.

Funnily, *if* B has gotten hold of the drive, then A could actually mount 
it (as a network drive) from B. The situation is really *that* symmetric. 
That's FireWire for you...

(As another demonstration, plug an iSight into B and start iChat on A. 
It'll see the iSight as locally attached, and will happily use it if B 
isn't. All one big happy family of devices.)

As to a solution - I don't know a "fool proof" one. Mac OS X likes to treat 
FireWire external drives as if they belong to a logged-in user, which means 
it often unmounts them when you log out. You should be safe if you 
disconnect the A-B "network" cable before rebooting A, and plug it back in 
when A has "taken" the drive again. (That may be after logging in, if you 
have auto-login disabled.)

Cheers
  -- perry

--On August 27, 2005 10:34:59 PM -0700 Sims David <dmsims at mindspring.com> 
wrote:

> Hello,
> I have two G4 gigabits networked via firewire.  Computer A has an
> external firewire drive wired to it, that is used by both computers  for
> backups. Computer B accesses the drive by connecting to A and  mounting
> it.
>
> Here is the problem....
>
> Often times, the external drive disappears from computer A's desktop.  It
> does not show in the drive utility, but it does show up in system
> profiler. Even when it is not accessible from computer A, computer B  can
> mount it and use it.  If the firewire cord is unplugged and  plugged back
> in, the drive appears on computer A's desktop.
>
> Is there a way to get the drive accessible, without unplugging/re-
> plugging the firewire cord?
> Thanks,
> David
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Perry The Cynic                                             perry at cynic.org
To a blind optimist, an optimistic realist must seem like an Accursed Cynic.
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