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Port Multiplier Compatibility
When configured as a set of individual drives and connected to a SATA or an
eSATA host adapter, the Port Multiplier will only work with a Port Multiplier aware
host. This includes setting up the unit with more than one array. Identify your host
controller and check with its hardware manufacturer if you are unsure. Addonics
offers several Port Multiplier aware host adapters.
Using identical drives for all settings other than JBOD or LARGE is strongly
recommended. Creating a LARGE array using drives that have different proper-
ties will use all space on all members, and performance will match that of the
member in use during any particular I/O operation. Creating a RAID using drives
that are not all the same size will result in all members using only as much space
as the smallest member. Creating a RAID using drives that have different perfor-
mance will degrade the overall performance of the array.
Port Multiplier Modes
JBOD Mode (Individual Drives)
Number of drives: at least 1
Unit capacity: N/A (100% of each individual drive)
Spares: no
Fault tolerance: none
JBOD mode offers all connected units to the host adapter, no RAID is defined at
all.
NOTE: JBOD mode requires a SATA controller featuring Port Multiplier support for
eSATA connections.
NOTE: Optical drives can only be configured as JBOD using an eSATA connec-
tion.
RAID 0 (Stripe set)
Number of drives: at least 2
Unit capacity: size of each member times number of members.
Spares: no
Fault tolerance: none - if any member is lost all data is lost.
RAID 0 “stripes” the file system across the array by placing “chunks” of data
sequentially between drives in a specific order.
RAID 1 or 10 (Mirror set, Stripe of mirror sets)
Number of drives: 2 (RAID 1) or 4 (RAID 10).
Unit capacity: size of one member (RAID 1) or size of two members (RAID 10).
Spares: yes – if EZ mode is not disabled and 3 (RAID 1) or 5 (RAID 10) drives are
present, the array will be initialized with a spare.
Fault tolerance: RAID 1 can withstand the loss of one drive without losing data.
RAID 10 can withstand the loss of one drive from each mirror set without losing
data.
RAID 1 works by duplicating the exact same data on two drives.
RAID 10 works by using two RAID 1 sets configured as members of a RAID 0.
Disks 1 and 2 are mirrored, disks 3 and 4 are mirrored, and the two mirror sets
are striped together.