Hi-Rely RAIDPac-II Manuale operativo - Pagina 12

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*LARGE

*CLONE

mirrored sets in one striped set (minimum four

disks; even number of disks) provides fault

tolerance and improved performance but increases

complexity. RAID 1+0 creates a striped set from a

series of mirrored drives. The array can sustain

multiple drive losses so long as no mirror loses all

its drives. With 4 drives, this means that any one

drive can fail. But if two drives fail, the whole

RAID will break unless those two drives happen

to be in the same mirror. RAID 10 offers better

protection than RAID 5, 3 or RAID 1 because

there is the added possibility of survival if two

drives fail (under the right combination).

RAID 3 (byte-level striping with dedicated

parity), data is striped such that each sequential

byte

is on a different disk. Parity is calculated

across corresponding bytes on disks and stored on

a dedicated parity disk. Higher data transfer rates

are possible. A single drive failure is tolerated.

RAID group controller will rebuild the failed

drive upon replacement automatically.

RAID 5 (block-level striping with distributed

parity) distributes parity along with the data and

requires all drives but one to be present to operate;

drive failure requires replacement, but the array is

not destroyed by a single drive failure. Upon drive

failure, any subsequent reads can be calculated

from the distributed parity such that the drive

failure is masked from the end user. The array will

have data loss in the event of a second drive

failure and is vulnerable until the data that was on

the failed drive is rebuilt onto a replacement drive.

LARGE: The designated drives are concatenated

into a single large volume. The difference

between LARGE and RAID0 is that RAID 0

offers better performance but at the cost of

flexibility. LARGE can concatenate drives of

different sizes and use the complete space of all

drives.

HOWVER, LIKE RAID 0, LARGE CAN

BECOME UNUSABLE IF JUST A SINGLE

DRIVE FAILS.

Clone: The designated drives are mirror copies of

each other.