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Managing the Virtual I/O Cache  



This section describes how to manage VIOC. It describes the following tasks:

Task Section
Selecting VIOC on an Alpha or I64 system
Selecting VIOC on an Alpha or I64 System
Controlling the size of the cache
Controlling the Size of the Cache
Monitoring performance
Displaying VIOC Statistics

The virtual I/O cache is a clusterwide, write-through, file-oriented, disk cache that can reduce the number of disk I/O operations and increase performance. The purpose of the virtual I/O cache is to increase system throughput by reducing file I/O response times with minimum overhead. The virtual I/O cache operates transparently of system management and application software, and maintains system reliability while it significantly improves virtual disk I/O read performance.

Understanding How the Cache Works  

The virtual I/O cache can store data files and image files. For example, ODS-2 disk file data blocks are copied to the virtual I/O cache the first time they are accessed. Any subsequent read requests of the same data blocks are satisfied from the virtual I/O cache (hits) eliminating any physical disk I/O operations (misses) that would have occurred.

Depending on your system work load, you should see increased application throughput, increased interactive responsiveness, and reduced I/O load.


NoteApplications that initiate single read and write requests do not benefit from virtual I/O caching as the data is never reread from the cache. Applications that rely on implicit I/O delays might abort or yield unpredictable results.

Several policies govern how the cache manipulates data, as follows:
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