[Info-vax] free shell accounts?

[Phillip Helbig undress to reply]

In article <m9r1cq$p2q$1 at speranza.aioe.org>, Stan Radford
<sradford at noemail.net> writes: 

> > There are several possibilities, but probably most clusters have all 
> > disks mounted on all nodes,
> 
> What does that mean actually? Does that mean they share physical disks
> because they all have physical connections or something else? 

There are several possibilities.  Some perform better than others.  Some 
disks can be connected to more than one controller.  Another possibility 
is for each disk to have a local connection to only one machine, then 
these are "served" over the network to the other machines.  Often, one 
wants volume-shadowing to guard against disk failure.  In this case, if 
one member is on one node and the other on another node, then in the 
case of node failure the virtual disk (the shadow set, now with one less 
member) is still available.

> If it's
> multiple boxes connected to one or more disk arrays that make sense. If not
> I don't understand how it can work.

It's magic!  It's not a trick, it's VMS!  :-)

> As long as they're all physically attached to the same drives. But if
> they're attached to network drives and the owning box goes down then there's
> a problem.

Not if the disks the applications see consist of more than one physical 
disk and/or connected to more than one node.