Tiered Storage—Balancing Application Service with PCFE Requirements 225
For example, a storage system can implement MAID Level 0 (no real
energy savings, no impact on performance) for active data. For less active
data, an administrator can choose a user-selectable setting to transition the
storage system to MAID Level 1, in which power is reduced by retracting
HDD read/write heads. For even more power savings, a HDD or RAID
group or some other unit of storage granularity can be put into a MAID
Level 2 mode, in which the speed of the drive platters is reduced. For the
most power savings, the administrator can select MAID Level 3, in which a
HDD or the RAID group is completely powered down or put into a sus-
pended/standby/sleep mode. Second-generation ...