<<Can someone out there give me a better understanding as to what is the
best solution to accomplish the following (I have talked to four
different people this morning and basically have 4 different
definitions)?

Objective: Incorporate a disk subsystem-28GB, that is up real time all
the time even if a mechanical failure (disk/power/fan or interface) were
to occur.

Two alternatives have been bantered about:

A3312A "HA disk subsystem w/hot plugablecooling fans,power supply and 2
SCSI buses w/4.1MB disk drive modules.

A3232A HA disk Array Mod 20 w/addl power supply, 2nd processor, w/16MB
cache and battery backup.

What is the difference between Hot plugable and hot swapable?>>


"Hot pluggable" is essentially a hardware issue: the device is
constructed so that it can safely be disconnected from or connected to
the system without powering down either the system or device. It
generally means that the device connectors are constructed such that
ground lines connect first/disconnect last, then signal lines, and power
conductors are the first to disconnect and last to connect. In some
cases, it also ensures that different power supplies are
connected/disconnected in the proper sequence; some, generally older,
semiconductor designs would destroy the components if a required "bias"
voltage was not supplied before the operating power. Basically, connector
sequencing ensures that the device can be connected to/disconnected from
a "hot" system without damaging either the system or the device.

"Hot swappable" is the next step, where the system software (or firmware,
such as on an array controller) is able to recognize and properly handle
the (dis)appearance of the hot pluggable device. If you check the HP page
on the 3311/2A arrays, it says that you have to be using Mirrored Disk/iX
to make use of the hot-pluggable capability of the hardware (well, that's
not really what it says, but it's what it *should* say). The hardware, by
itself, is hot pluggable. However, the system has to have
hot-replacement-aware software, i.e. Mirrored Disk/iX, for the array
drives to become hot swappable.

Steve