LaCie 131018 - StorView Snapshot - Mac, Руководство пользователя

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Configuring a Storage Solution
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RAID Level 1 RAID 1 is defined as disk mirroring where one drive is an exact copy of
the other. RAID 1 is useful for building a fault-tolerant system or data
volume, providing excellent availability without sacrificing
performance. However, you lose 50 percent of the assigned disk
capacity. Read performance is somewhat higher than write
performance.
RAID Level 5 RAID 5 is defined as disk striping with parity where the parity data is
distributed across all drives in the volume. Normal data and parity data
are written to drives in the stripe set in a round-robin algorithm. RAID 5
is multi-threaded for both reads and writes because both normal data
and parity data are distributed round-robin. This is one reason why
RAID 5 offers better overall performance in server applications.
Random I/O benefits more from RAID 5 than does sequential I/O, and
writes take a performance hit because of the parity calculations. RAID
5 is ideal for database applications.
RAID Level 6 RAID-6 is the same as RAID-5 except that it uses a second level of
independently calculated and distributed parity information for
additional fault tolerance. This extra fault tolerance provides data
security in the event two drives fail before a drive can be
replaced. RAID-6 provides greater fault tolerance than RAID-5. There
is a loss in write performance with RAID-6 when compared to RAID-5
due to the requirement for storing parity twice for each write operation.
A RAID-6 configuration also requires N+2 drives to accommodate the
additional parity data, which makes RAID-6 require more raw
capacity than RAID-5 for an equivalent useable storage capacity.
RAID Level 10 RAID 10 is defined as mirrored stripe sets or also known as RAID 0+1.
You can build RAID 10 either directly through the RAID controller
(depending on the controller) or by combining software mirroring and
controller striping, or vice versa (called RAID 01).
RAID Level 50 This RAID level is a combination of RAID level 5 and RAID level 0.
Individual smaller RAID 5 arrays are striped, to give a single RAID 50
array. This can increase the performance by allowing the controller to
more efficiently cluster commands together. Fault tolerance is also
increased, as one drive can fail in each individual array.
Stripe The process of separating data for storage on more than one disk. For
example, bit striping stores bits 0 and 4 of all bytes on disk 1, bits 1 and
5 on disk 2, etc.
Stripe Size This is the number of data drives multiplied by the chunk size.
Sub-array In RAID 50 applications, this is the name given when individual RAID
5 arrays that are striped together. Each sub-array has one parity drive.
Unassigned Free Space The controller keeps a map of all the space that is not assigned to any
logical drive. This space is available for creation or expansion. Each
unassigned region is individually listed.
Term Description