Browse Prior Art Database

Optimal Seek-Speed versus Power Tradeoff in Disk File Systems

IP.com Disclosure Number: IPCOM000115736D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Serrano, J: AUTHOR

Abstract

Disclosed is a control scheme that can optimally trade off the increase of the Weighted Average Access Time (WAAT) of the system for a decrease in the weighted average energy required for seeking. This tradeoff can be determined online, governed either by a user command, or by internally generated statistics.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Optimal Seek-Speed versus Power Tradeoff in Disk File Systems

      Disclosed is a control scheme that can optimally trade off the
increase of the Weighted Average Access Time (WAAT) of the system for
a decrease in the weighted average energy required for seeking.  This
tradeoff can be determined online, governed either by a user command,
or by internally generated statistics.

      With regard to the weighted average energy versus WAAT problem,
was made in (*).  If the angular position of the data is known, then
the seek time plus the latency is constant.  (The seek time plus the
latency is called the access time.)  This scheme gives the lowest
average energy without increasing the average access time.  If lower
energy levels are required, the average access time must be
increased.  The key observation is that for each seek, the next
fastest access time is one rev (the revolution time of the disk)
longer.

      Suppose the weighted average energy for the present seek scheme
is WAE0.  The procedure to find the seek scheme that provides the
smallest WAAT while constraining the weighted average energy to be
less than the limit Plim is: For each seek Sij of rotational
offset i and length j, determine the energy Pij required.  Also
determine the energy Qij required if the seek time is increased by
one rev.  Determine which seek Sij1 has the largest energy savings
when done more slowly.  Now when performing seek Sij1, seek so as to
arrive in the minimal access time plus on...