Preventing fast wear-out of flash cache with an admission control policy

Eunji Lee, Hyokyung Bahn

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Recently, flash cache is widely adopted as the performance accelerator of legacy storage systems. Unlike other cache media, flash cache should be carefully managed as it has peculiar characteristics such as long write latency and limited P/E cycles. In particular, we make two prominent observations that can be utilized in managing flash cache. First, a serious worn-out problem happens when the working-set of a system is beyond the capacity of flash cache due to excessively frequent cache replacement. Second, more than 50% of data has no hit in flash cache as it is a second level cache. Based on these observations, we propose a cache admission control policy that does not cache data when it is first accessed, and inserts it into the cache only after its second access occurs within a certain time window. This allows the filtering of data disruptive to flash cache in terms of endurance and performance. With this policy, we prolong the lifetime of flash cache 2.3 times without any performance degradations.

Original languageEnglish
Pages (from-to)546-553
Number of pages8
JournalJournal of Semiconductor Technology and Science
Issue number5
StatePublished - Oct 2015

Bibliographical note

Publisher Copyright:
© 2015, Institute of Electronics Engineers of Korea. All rights reserved


  • Admission control
  • Flash cache
  • Flash memory
  • LRU
  • Replacement policy


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