IBM 866251Y - Netfinity 5500 M20, Руководство по техническому обслуживанию аппаратной части, Страница: 76 / 386

The ServeRAID adapters and controllers support RAID
level-0, RAID level-1, Enhanced RAID level-1, and RAID
level-5.
RAID level-0:
RAID level-0 stripes the data across all
the drives in the array. This offers substantial speed
enhancement, but provides for no data redundancy. RAID
level-0 provides the largest capacity of the RAID levels
offered, because no room is taken up for redundant data
or data-parity storage.
The following illustration shows data arranged in an array
of three hard disk drives defined as one RAID level-0
logical drive. Notice that the data is striped across all the
drives in the array, but no copies of the data or parity
information is stored.
A hard disk failure within the array results in loss of data in
the logical drive assigned RAID level-0, but
only in that
logical drive. If there are logical drives assigned RAID
level-1 or level-5 in the same array, they will not lose data.
Note
The ServeRAID controller automatically assigns RAID
level-0 to all logical drives in an array containing only
one hard disk drive.
When you replace a failed drive, the ServeRAID controller
can rebuild all the RAID level-1 and RAID level-5 logical
drives automatically onto the replacement hard disk drive.
However, any data stored in a failed RAID level-0 logical
drive is lost.
Though the risk of data loss is present, you might want to
assign RAID level-0 to one of the logical drives to take
advantage of the speed offered with this RAID level. You
could use this logical drive to enter data that is backed up
each day and for which safety is not of primary
importance, that is, data that can be easily re-created.
You also might want to use a RAID level-0 logical drive
when the work being done requires maximum capacity.
. . . . . .
Stripe 1
Block 1 Block 2 Block 3
Stripe 2
Block 4 Block 5 Block 6
Stripe 3
Block 7 Block 8 Block 9
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