USENIX 2002 Annual Conference - Technical Program Abstract
My cache or yours? Making storage more exclusive
Theodore M. Wong
Carnegie Mellon University, Pittsburgh, PA
Modern high-end disk arrays often have several gigabytes of cache RAM.
Unfortunately, most array caches use management policies which duplicate
the same data blocks at both the client and array levels of the cache
hierarchy: they are inclusive. Thus, the aggregate cache behaves as
if it was only as big as the larger of the client and array caches, instead
of as large as the sum of the two. Inclusiveness is wasteful: cache RAM
We explore the benefits of a simple scheme to achieve exclusive
caching, in which a data block is cached at either a client or the disk
array, but not both. Exclusiveness helps to create the effect of a single,
large unified cache. We introduce a DEMOTE operation to transfer data
ejected from the client to the array, and explore its effectiveness with
simulation studies. We quantify the benefits and overheads of demotions
across both synthetic and real-life workloads. The results show that we can
obtain useful--sometimes substantial--speedups.
- View the full text of this paper in
The Proceedings are published as a collective work, © 2002 by the USENIX Association. All Rights Reserved. Rights
to individual papers remain with the author or the author's employer.
Permission is granted for the noncommercial reproduction of the complete
work for educational or research purposes. USENIX acknowledges all
trademarks within this paper.
- If you need the latest Adobe Acrobat Reader, you can download it from Adobe's site.
- To become a USENIX Member, please see our Membership Information.