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XRAY: A NonInvasive Exclusive Caching Mechanism for RAIDs Lakshmi N. Bairavasundaram, Muthian Sivathanu,
 

Summary: X­RAY: A Non­Invasive Exclusive Caching Mechanism for RAIDs
Lakshmi N. Bairavasundaram, Muthian Sivathanu,
Andrea C. Arpaci­Dusseau, and Remzi H. Arpaci­Dusseau
Computer Sciences Department, University of Wisconsin­Madison
Abstract
RAID storage arrays often possess gigabytes of RAM for
caching disk blocks. Currently, most RAID systems use LRU
or LRU­like policies to manage these caches. Since these array
caches do not recognize the presence of file system buffer caches,
they redundantly retain many of the same blocks as those cached
by the file system, thereby wasting precious cache space. In this
paper, we introduce X­RAY, an exclusive RAID array caching
mechanism. X­RAY achieves a high degree of (but not perfect) ex­
clusivity through gray­box methods: by observing which files have
been accessed through updates to file system meta­data, X­RAY
constructs an approximate image of the contents of the file system
cache and uses that information to determine the exclusive set of
blocks that should be cached by the array. We use microbench­
marks to demonstrate that X­RAY's prediction of the file system
buffer cache contents is highly accurate, and trace­based sim­

  

Source: Arpaci-Dusseau, Andrea - Department of Computer Sciences, University of Wisconsin at Madison
Arpaci-Dusseau, Remzi - Department of Computer Sciences, Department of Computer Sciences, University of Wisconsin at Madison

 

Collections: Computer Technologies and Information Sciences