OWC MERCURY RACK PRO Assembly Manual & User Manual page 7

Combine (SPAN) Mode
Switch setting: UP-DOWN-UP
The drives appear as one large volume. The total capacity depends on the drives
used; you can use different capacities. Combine (SPAN) is an array (but not a
RAID) in which the data is written sequentially across the drives. This combines
the drives' capacities, but provides no performance or data redundancy benefits.
RAID 0 "Drive Striping" Mode
Switch setting: UP-UP-UP
The drives appear as one large volume with a size equal to the combined
capacities of all the drives in the array. RAID 0 is used when speed is the primary
objective, but it does not provide any type of data protection. Data is alternated
very quickly across two or more drives to gain speed by distributing the workload.
This allows for the fastest data transfer rates, since data is written without pausing
to check parity information. However if one drive fails, the whole array can become
corrupted and data will be lost. Always maintain a backup of your data!
RAID 1 "Drive Mirroring" Mode (2 Drives Installed)
Switch setting: UP-UP-DOWN
The drives appear as one volume with a size equal to the capacity of one installed
drive. RAID 1 copies (or "mirrors") a set of data from the first drive to the second
drive. This is useful when reliability and backup are more important than capacity
or speed. If one drive fails, it can be replaced and the data rebuilt.
RAID 10 "Drive Mirroring with Striping" Mode (4 Drives Installed)
Switch setting: UP-UP-DOWN
The drives appear as one volume with a size equal to the combined capacities of
half of the drives in the array. RAID 10 uses a combination of striped and mirrored
volumes. If one drive fails, it can be replaced and the data rebuilt.
RAID 3 "Drive Striping with Dedicated Parity" Mode
Switch setting: UP-DOWN-DOWN
The drives appear as one volume with a size equal to the combined capacities of
all the drives in the array, minus one drive. RAID 3 uses byte-level striping, with
parity information located on a dedicated parity drive. Very fast performance can
be achieved with RAID 3 while also maintaining fault protection, so if one drive
fails, it can be replaced and the data rebuilt.
RAID 5 "Drive Striping with Distributed Parity" Mode
Switch setting: DOWN-UP-DOWN
The drives appear as one volume with a size equal to the combined capacities of
all drives in the array, minus one drive. RAID 5 uses block-level striping with parity
data distributed across all disks. It provides a good balance between performance
and data integrity. If one drive fails, it can be replaced and the data rebuilt.
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OWC Mercury Rack Pro Introduction