NonStop S-Series Server Description Manual (G06.24+)

Introduction

HP NonStop S-Series Server Description Manual—520331-003

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Fault-Tolerant Disk Access

Multiple disk drives are provided for within the processor enclosure. A single SCSI bus

can support up to eight of these drives, and there are two such buses.

Both processors in the enclosure have fault-tolerant access to all installed drives. That

is, either processor can access the drives through either of the two multifunction I/O

boards (MFIOBs).

Figure 1-6 illustrates the basic I/O configuration for the two SCSI buses. Note that one

MFIOB provides access through the X router, and the other MFIOB provides access

through the Y router.

In addition to fault-tolerant disk access paths, fault tolerance for databases can be

augmented by the use of mirrored volumes. This optional access method maintains

duplicate data on two separate physical volumes. Thus, whenever data is read from

the files, either volume can be accessed because they contain identical information. All

data written out to the files is automatically written on both disk volumes.