Mode Category Description Default MCU/RCU
Note: For DT pools (including those with active flash
attribute), the average of parity group usage rates is
calculated per tier.
Examples:
(1) In a DP pool, if the usage rates of PG1, PG2, and PG3
are 50%, 40%, and 30% respectively, it is not determined
as unbalanced.
Because the average parity group usage rate is (50%＋
40%＋ 30%) / 3 ＝ 40% and the difference in the rate
between each parity group and the average is 10% at the
maximum.
(2) In a DP pool, if the usage rates of PG1, PG2, and `G3
are 80%, 40%, and 30% respectively, it is determined as
unbalanced.
Because the average parity group usage rate is (80%＋
40%＋ 30%) / 3 ＝ 50% and the difference in the rate
between each parity group and the average is 30% at the
maximum.
(3) In a DT pool, if the usage rates of PG1, PG2, and PG3
are 80% (SSD), 40% (SAS15K) and 30% (SAS15K), it is
not determined as unbalanced because:
- the average parity group usage rate of Tier1 is (80%) / 1
＝ 80% and the difference in the rate between the parity
group and the average is 0%.
- the average parity group usage rate of Tier2 is (40%＋
30%) / 2 ＝ 35% and the difference in the rate between
the parity group and the average is 5% at the maximum.
Note:
(1) The mode is applied when balancing the usage rate is
required at a customer site where the usage rate is not
even.
SOM details
This section provides detailed information for several of the SOMs described
in the above table.
Details for SOM 15
Table 33 SOM 15 functions
Operation with Mode 15 ON
Operation with Mode 15 OFF
Upper limit for retry of drive is reduced from 2 sec to 0.5
sec.
Upper limit for retry of drive is 2 sec
176 System option modes
Hitachi Virtual Storage Platform G1000, G1500, and Virtual Storage Platform F1500 Hardware Guide
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