Руководство Пользователя для Edge10 DAS401
2.3 RAID
LEVELS
2.3.1 DISK STRIPING (RAID 0)
Striping is a performance-oriented, non-redundant data mapping technique. While Striping is discussed as a
RAID Group type, it is does not provide any fault tolerance. With modern SATA and ATA bus mastering
technology, multiple I/O operations can be performed in parallel, enhancing data throughput. Striping arrays use
multiple disks to form a larger virtual disk. The figure below illustrates a three-disk stripe set. Stripe one is written
to disk one, stripe two to disk two, and so forth. RAID 0 sets can be comprised of two, three, or four drives. If the
sizes of the disk segments are different, the smallest disk segment will limit the overall size of the RAID Group.
Stripe0
Stripe1
Stripe2
Stripe3 Stripe4 Stripe5
Stripe6
Stripe9
Stripe7
Stripe10
Stripe8
Stripe11
2.3.2 DISK MIRRORING (RAID 1)
Disk mirroring creates an identical twin for a selected disk by having the data simultaneously written to two disks.
This redundancy provides instantaneous protection from a single disk failure. If a read failure occurs on one drive,
the system reads the data from the other drive. RAID 1 sets are comprised of two drives, and a third drive can be
allocated as a spare in case one of the drives in the set fails. If the sizes of the disk segments are different, the
smallest disk segment will limit the overall size of the RAID Group.
Block 0
Block 1
Block 2
Block 3
Block 0
Block 1
Block 2
Block 3
2.3.3 DISK MIRRORING AND STRIPING (RAID 10)
RAID 10 combines the features of both RAID 0 and RAID 1. Performance is provided through the use of Striping
(RAID 0), while adding the fault tolerance of Mirroring (RAID 1). The implementation of RAID 10 requires four
drives. The drives are assigned as two sets of striped pairs.
The data is written to RAID Group A, which is mirrored (RAID 1) and provides data redundancy. Alternating
blocks of data are then striped across another RAID 1 mirrored set, shown as Set B in the figure above. This
provides improved speed.
Under certain circumstances, a RAID 10 set can sustain multiple simultaneous drive failures.
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DAS401 User’s Manual
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