Figure 13: Driver and system organization
Storage bus filter driver
The storage bus filter driver is named
HPtapeFailover_filt
and manages the OS notifications
indicating that devices have been added or removed. The storage bus filter driver bus enumerator is
usually "PCI". It attaches as an upper filter to all HBA drivers. It then monitors the creation of raw devices,
looking for supported failover capable devices. Requests to all other devices are passed through
unchanged. When a supported device is recognized, the hardware ID of the device is changed to a value
that the upper device driver will recognize, but that the rest of the system will not. The special hardware
ID prevents the standard tape class driver from attaching to the raw paths.
Storage bus filter driver
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