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Chapter 4: Subsystem Connection and Operation
Subsystem Connection and Operation 4-17
• This is a direct-attached configuration showing four (4) host computers
sharing the capacity in one (1) RAID subsystem. Disk drives in the
enclosure can be configured into one or more arrays, and made available
through individual host ports.
• Each configured array (logical drive) is separately mapped (or associated)
with more than one host ID/LUN. A logical configuration of drives may
appear as two array volumes to the host, and the multi-path management
software on the host should recognize them as access routes to the same
storage volume.
• In the sample diagram above, up to two IDs may appear through a host link.
To avoid access contention, you will need access management provided by
3
rd
party software.
• If a RAID controller fails or a data path is disconnected, the host computer
can still access the array. By associating an array with IDs on two different
host buses and two different RAID controllers, the host computer can
access the array in the event of single component failure.
• If Controller A fails, Controller B will take over to eliminate any downtime
for high-availability applications.
• Operating system(s) might boot from the array. Operating using a protected
capacity decreases the chance of server downtime. Each server may use
separate capacity volumes or share volumes using file locking or access
management utilities.
• Depending on I/O characteristics, each configured array should be properly
optimized either for Random or Sequential I/Os.
• You may also partition a logical capacity into two or more volumes and let
each server access separate partitions.