RAID and Subsystem Architectures
Assigning Hosts to Storage
Drive Assignment: Host Level
Logical Disks SCSI LUNs Physical Disks
Host A 5 x 1GB 5 x 1GB
Drive D (2 GB)
SCSI ID 3
Drive E (500 MB)
SCSI ID 4
Drive F (500 MB)
SCSI ID 1
1GB
1GB
1GB
1GB
1GB
SAN
Host B
Drive D (1GB)
SCSI ID 2
Drive E (1GB) SCSI ID 0
JBOD
Volume Manager HBA Utility
LUN Mapping
When we use a JBOD the Host Bus Adapter, HBA, has the ability to discover
all the available disks. We will look at SAN Fabric options for restricting
visibility in a later module.
If the host volume manager sees all disks, then we have a possible situation
where data could be written to the same disks without any knowledge of any
other data that has been written to that disk. This is most likely to cause data
corruption by overwriting data that has already been written to that disk.
The HBA configuration utility supports LUN Mapping. This allows us to
configure which discovered disks are usable by the host volume manager and
creates a map of which disks are advertised through, Mapped, to the volume
manager and which disks are blocked from being advertised through.