Raid Modes; Drive Failure - OWC Mercury Elite Pro Dual Assembly Manual & User Manual

2.3.2 RAID Modes

Independent Drive Mode:
Each drive will appear individually without being combined. If you are using drives of
differing capacity and model, or if you are using only one drive, this is the mode to use.
NOTE: Due to the incomplete support in OS X for the chipsets used in the Mercury
Elite Pro Dual, independent drive mode has the following limitations:
1. When connected over Thunderbolt in OS X 10.8.3 and earlier, only HDD2 appears.
Independent drive mode does not have this limitation when used over USB or when
used in OS X 10.8.4 and later.
2. When two hard drives are installed, only HDD2 will be available as a startup drive in
OS X. This happens in all versions of OS X and with both Thunderbolt and USB. HDD1
can be used normally after the computer has started; HDD1 is only unavailable
during the startup process. If only one drive is installed in the Mercury Elite Pro Dual,
it can be used in either the HDD1 or HDD2 position and it will be available as a
startup drive.
Span Mode:
The drives show up as one large single volume. The total size will depend on the drives
installed; you can use drives of different capacities. A span is a configuration (not RAID) in
which the data is written sequentially across the drives. This combines the capacities of
the drives, but it does not provide any performance or redundancy benefits.
RAID 0 "Drive Striping" Mode:
The drives show up as one large single volume with a size equal to the combined capaci-
ties of both drives. RAID 0 is used when speed is the primary objective, but it does not
have any redundancy for protection. Data is alternated very quickly across both drives
to gain speed by distributing the workload. This allows for the fastest data transfer rates,
but 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:
The drives show up as one volume with a size equal to the capacity of one of the two
drives used in the array. RAID 1 copies (or "mirrors") a set of data from the first drive to
the second drive. This is useful when reliability and redundancy are more important than
capacity. When one drive fails, it can be replaced and the data will be rebuilt automatically.

2.4 DRIVE FAILURE

In the event that one of the drives fails, the corresponding drive LED will turn solid red. If
the Mercury Elite Pro Dual was configured as a RAID 0 or span, the data on the array is lost
and the volume cannot be used. In a span, only the data stored on the failed drive is lost,
although data recovery software will be required to recover the data from the other drive in
the span. If the drives were configured independently, then the data on the drive that did
not fail will remain intact.
OWC DIGITAL - MERCURY ELITE PRO DUAL
10
DEVICE SETUP