Abstract
Thermal-aware design of disk drives is important because high temperatures can
cause reliability problems. Dynamic Thermal Management (DTM) techniques have
been proposed to operate the disk at the average case temperature, rather than at the
worse case by modulating the activities to avoid thermal emergencies. The thermal
emergencies can be caused by unexpected events, such as fan-breaks, increased inlet
air temperature, etc. One of the DTM techniques is a delay-based approach that
adjusts the disk seek activities, cooling down the disk drives. Even if such a DTM
approach could overcome thermal emergencies without stopping disk activity, it suffers
from long delays when servicing the requests. Thus, in this chapter, we investigate
the possibility of using a multispeed disk-drive (called dynamic rotations per
minute (DRPM)) that dynamically modulates the rotational speed of the platter for
implementing the DTM technique. Using a detailed performance and thermal simulator
of a storage system, we evaluate two possible DTM policies (- time-based and
watermark-based) with a DRPM disk-drive and observe that dynamic RPM modulation
is effective in avoiding thermal emergencies. However, we find that the time
taken to transition between different rotational speeds of the disk is critical for the
effectiveness of the DRPM based DTM techniques.