Dear Managers,
The essence of my question was how to share storage space in a RAID Array
[N]000 via an UltraSCSI Hub or FibreChannel in a non-clustered
configuration. Perhaps it is not a very common setup because I didn't
really get any responses to my questions. I did manage to get ahold of an
engineer at Compaq/Digital who was able to provide me with some answers.
Questions:
> A) Is it true that the RA3000 can only be shared via an UltraSCSI Hub if it
> is being used in a cluster and/or only with Windows NT?
according to the engineer this is true, the RAID Array 3000 will only allow
for sharing only in a clustered environment.
> B) If I share the "storage subsystem" in a non-clustered configuration (as
> permitted by the RA7000), how flexible can I be about switching disks
> between one machine and the other?
Apparently, if the disksets on the RA 7000 are defined without any access
restrictions, even in a non-clustered configuration they can be switched
between machines by simply unmounting/mounting them on any machine on the
hub. This is, for now, very similar to how it works in a clustered
environment as well. However, in Tru64 Unix v5.0, there will be a new
filesystem, the Clustered File System (CFS), that will allow a partition to
mounted simultaneously on more than one machine in a cluster (i.e. vaguely
resembling NFS).
> C) Would I gain anything about going to Fibre Channel (other than the
> obvious speed increase)? Or is the problem with sharing more at the OS
> level? What is the status of Fibre Channel support in Tru64 Unix?
Compaq has a series of new Fibre Channel RAID Arrays (the 8000 and 12000)
that are supported on Tru64 Unix. The functionality of the sharing of disks
among machines will be very similar with Fibre Channel as it was with the
UltraSCSI Hub. Fibre Channel will allow a transfer rate approximately
double or triple that of the an UltraSCSI bus (60-70 versus 25 MB/sec).
With the RA 8000 and 12000 and Tru64 Unix one must use a Fibre Channel
switch not a hub (if I understood correctly). This is more costly, but
allows all the machines connected to the array to get the same maximum
throughput to the RAID array (instead of sharing the bandwidth as on a
hub).
I did have one response from Kenneth Forward who suggested this easier,
lower-cost solution (that we are now considering as well):
"It all depends on how you define a SAN. It may not suffice for your
purpose, but if you simply put a second NIC in each of your machines, and
connect these via a switch under their own subnet, then your NFS/backup
traffic can be isolated. This may not greatly improve your NFS/backup
performance, but it will definately prevent said traffic from clobbering
your users' interactive experience."
cheers,
kevin reardon
Osservatorio Astronomico di Capodimonte
Received on Thu Jun 10 1999 - 11:34:07 NZST