User guide

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RAID Modes
The Secure NAS unit supports one drive in JBOD Mode, several types of RAID
and some non-RAID drive sets. Each configuration has different properties and
requirements, as follows:
JBOD Mode (Individual Drives)
Number of drives: 1
Unit capacity: N/A
Spares: no
Fault tolerance: none
JBOD mode may only be used with one drive installed in the Secure NAS unit.
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 (see note).
RAID 0 “stripes” the file system across the array by placing “chunks” of data
sequentially between drives in a specific order.
NOTE: Risk of data loss compared to a single drive multiplies by the number of
members in a RAID 0.
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.
RAID 3 (Stripe set with dedicated parity)
Number of drives: at least 3
Unit capacity: size of one member times number of members minus one.
Spares: yes
Fault tolerance: can withstand the loss of one drive without losing data.
RAID 3 works by striping data for individual I/O blocks across all members
except one, which contains parity data for the stripe set computed internally by
the Port Multiplier. In the event of failure, the missing information can be
calculated using the parity information.