Excellent document. I will need to study it for a bit. Much of the
information I am looking for can be gleaned from this document.

I see why we saw opposite speed differentials in comparing SAN versus
RAID. Our SAN runs on a gigabit fiber line, with 256 GB of cache RAM.
It is much faster than local RAID since you rarely actually see the
physical DASD I/O overhead on the SAN. Propagation delay on a gigabit
fiber card can be as low as a few micro seconds, versus a few
milliseconds for physical I/O on a RAID array. Not all SAN solutions
are equal.

Regarding 24x7 - A few years back, a certain shop announced it had full
24x7 capability with auto-failover to a backup hot-site. It was tested
during peak production hours and no one noticed that the switchover had
occurred. Exactly one week after the announcement, the DASD unit with
the only copy of the failover program blew up (literally), and there was
no manual switch over mechanism. It took a week to get that company
back on line again. :o)

On Tue, 2005-02-08 at 19:38, Dalton Calford wrote:
>
>
> David,
>
> Have you read the "Some Solutions to Old Problems" document. Helen
> Borrie was kind enough to edit a bunch of my pondering on the subject of
> scalability.
> It covers some hardware and software design criteria depending upon the
> needs of the user. That document is getting dated, but, it does cover
> some of your requirements.