User Guide

16 NetWare Server Disks and Storage Devices Administration Guide
NetWare Server Disks and Storage Devices Administration Guide
103-000179-001
August 30, 2001
Novell Confidential
Manual 99a38 July 17, 2001
Drivers for Host Adapters and Storage Devices
All storage devices require drivers. The NetWare Peripheral Architecture
(NWPA) divides device drivers into two kinds: a custom device module
(CDM) that drives the device itself and a host adapter module (HAM) that
drives the adapter has been attached to. The following are two types of drivers:
 Custom Device Module (CDM)
CDMs drive storage devices, including autochangers, that are attached to
the host adapter bus.
CDMs are device-specific. For example, if there are three different types
of storage devices attached to the host adapter (such as a CD-ROM drive,
a SCSI hard drive, and an autochanger) then a specific CDM for each type
of device must be installed.
 Host Adapter Module (HAM)
A HAM is the driver component associated with the host adapter
hardware. HAMs provide the functionality to route requests to the bus
where a specified device is attached.
HAMs are adapter-specific. For example, if a third-party adapter is
installed in the server, a HAM developed specifically for that adapter
must be installed.
Loading HAMs and CDMs is much like loading other device drivers, but
instead of loading one .dsk file for both the adapter and device, you load one
.ham file for the adapter and one .cdm file for each type of device attached to
that adapter.
When you want to connect a new hardware device to the host bus adapter, you
need to load only the appropriate CDM for that hardware device (in addition
to the HAMs and CDMs already loaded, and assuming a compatible adapter
is installed).
Mirroring and Duplexing
You can protect the data mirroring or duplexing disk partitions.
Mirroring stores the same data on separate disks on the same controller
channel; duplexing stores the same data on separate disks on separate
controller channels. Duplexing can also use two different drivers. Duplexing
is the recommended method because two channels rarely fail simultaneously.