High Available Storage Systems (HASS) provide
two internal SCSI busses, each with their own connectors, power cords,
power supplies, and fans. This hardware redundancy, when combined
with software ing, can prevent most single point of failure problems.
HASS do not provide any RAID support on their own.
Pros and Cons of HASS
There are many advantages of systems protected
by HASS. These include disk storage modules that are hot-pluggable which means that the bus and
connectors are made so that the disk module can be inserted or removed
without removing the terminator for the array. All hardware modules
are easily removed from the front of the chassis. HASS do not have
the problems of previous disk configurations that required extra-long
F/W SCSI cables, the removal of the chassis from the cabinet, and
the removal of the cover before individual disk mechanisms can be
The negative side of HASS
is that operating system cooperation is still required when removing
a disk module from the HASS since the HASS does not provide any data protection or regeneration of data on a newly replaced
disk module. HASS is primarily a hardware protection strategy and
software mirroring is required to implement a mirroring scheme on
Recommended Uses of HASS
The HASS protection system is an excellent step
in preventing single points of failure and is recommended for systems
that must be available as much of the time as possible. Serviceguard
can employ HASS for additional data storage. See“Using Serviceguard”.