Silicon Graphics InfiniteStorage 4000 Series, Configuring And Maintaining

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Chapter 3: Configuration Concepts 49
Hosts A host is a computer that is attached to the storage array for accessing the volumes in
the storage array. The host is attached to the storage array through HBA host ports,
which are connectors on host bus adapter circuit boards. You can define specific
volume-to-LUN mappings to an individual host or assign the host to a host group that
shares access to one or more volumes. Hosts are identified by names or labels that
users choose. The host name can be any combination of alphanumeric characters,
hyphens, and underscores. The maximum length of the host name is 30 characters.
In addition to a host name, some script commands require you to identify a host by its
“type.” A host type identifies the operating system under which the host is running
(such as Windows, Solaris, or Linux). Specifying the host type lets the controllers in
the storage array adapt their behavior (such as LUN reporting and error conditions) to
the operating system of the host that is sending the information. Host types are
identified by a label or an index number that is generated by the controller firmware.
3
High-bandwidth mode
– RAID Level 3 stripes both user data and redundancy data (in
the form of parity) across the drives. The equivalent of the capacity of one drive is used
for the redundancy data. RAID Level 3 works well for large data transfers in applications,
such as multimedia or medical imaging, that write and read large sequential chunks of
data.
If a single drive fails in a RAID Level 3 volume group, all of the associated volumes
become degraded, but the redundancy data lets the data be reconstructed. If two or more
drives fail, all of the associated volumes fail, and all data is lost.
5
High I/O mode
– RAID Level 5 stripes both user data and redundancy data (in the form
of parity) across the drives. The equivalent of the capacity of one drive is used for the
redundancy data. RAID Level 5 works well for multiuser environments, such as
databases or file system storage, where typical I/O size is small, and a high proportion of
read activity exists.
If a single drive fails in a RAID Level 5 volume group, all of the associated volumes
become degraded, and the redundancy data permits the data to be reconstructed. If two or
more drives fail, all of the associated volumes fail, and all data is lost.
6
Data protection or continuous access mode
– RAID Level 6 stripes both user data and
redundancy data (in the form of parity) across the drives. A minimum of five drives are
required for a RAID Level 6 volume group. The equivalent capacity of two drives is used
for the redundancy data. Two different algorithms calculate redundancy data, which are
in the form of both a P parity and a Q parity.
RAID Level 6 works well for larger drive sizes. Recovery from a second drive failure in
the same volume group is possible. If two drives fail in a RAID Level 6 volume group, all
of the associated volumes become degraded, but the redundancy data permits the data to
be reconstructed. If three or more drives fail, all of the associated volumes fail, and all
data is lost.
RAID Level Configuration