Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Using High Availability Strategies

Using High Available Storage Systems (HASS)

Appendix A956

Using High Available Storage Systems (HASS)

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

mirroring, 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

replaced.

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

HASS.

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” on page 957.