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nection to every connected device. Each node on a Switched fabric uses an
aggregate throughput data path to send or receive data.
1.3.4 LUN Masking
LUN masking is a RAID system-centric enforced method of masking multiple
LUNs behind a single port. By using World Wide Port Names (WWPNs) of
server HBAs, LUN masking is configured at the RAID-array level. LUN mask-
ing also allows disk storage resource sharing across multiple independent
servers. A single large RAID device can be sub-divided to serve a number of
different hosts that are attached to the RAID through the SAN fabric with LUN
masking. So that only one or a limited number of servers can see that LUN,
each LUN inside the RAID device can be limited.
LUN masking can be done either at the RAID device (behind the RAID port) or
at the server HBA. It is more secure to mask LUNs at the RAID device, but
not all RAID devices have LUN masking capability. Therefore, in order to
mask LUNs, some HBA vendors allow persistent binding at the driver-level.
1.4 Array Definition
1.4.1 RAID Set
A RAID Set is a group of disks containing one or more volume sets. It has the
following features in the RAID subsystem controller:
1. Up to 128 RAID Sets are supported per RAID subsystem controller.
2. It is impossible to have multiple RAID Sets on the same disks.
A Volume Set must be created either on an existing RAID set or on a group
of available individual disks (disks that are not yet a part of an raid set). If
there are pre-existing raid sets with available capacity and enough disks for
specified RAID level desired, then the volume set will be created in the exist-
ing raid set of the user's choice. If physical disks of different capacity are
grouped together in a raid set, then the capacity of the smallest disk will
become the effective capacity of all the disks in the raid set.
Introduction
1-13
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