Item
Description
Description Data blocks are scattered to multiple disks in the same way as RAID 5 and two
parity disks, P and Q, are set in each row. Therefore, data can be assured even
when failures occur in up to two disk drives in a parity group.
Advantage RAID 6 is much more reliable than RAID 1 and RAID 5 because it can restore
data even when failures occur in up to two disks in a parity group.
Disadvantage The parity data P and Q must be updated when data is updated, RAID6 imposes
a write heavier than that on RAID 5, performance of the random writing is lower
than that of RAID 5 in the case where the number of drives makes a bottleneck.
LDEV striping across array groups
In addition to the conventional concatenation of RAID1 array groups (4D
+4D), the storage system supports LDEV striping across multiple RAID5
array groups for improved logical unit performance in Open-system
environments. The advantages of LDEV striping are:
• Improved performance, especially of an individual logical unit, due to an
increase in the number of drives that constitute an array group.
• Superior workload distribution: If the workload of one array group is
higher than another array group, you can distribute the workload by
combining the array groups, thereby reducing the total workload
concentrated on each specific array group.
The supported LDEV striping configurations are:
• LDEV striping across two RAID5 (7D+1P) array groups. The maximum
number of LDEVs in this configuration is 1000. See the following figure.
• LDEV striping across four RAID5 (7D+1P) array groups. The maximum
number of LDEVs in this configuration is 2000. See
Figure 13 LDEV
Striping Across 4 RAID5 (7D+1P) Array Groups on page 61.
Hardware architecture 59
Hitachi Virtual Storage Platform G1000, G1500, and Virtual Storage Platform F1500 Hardware Guide
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