Promise Technology 2-Year Extended Warranty for VessR2000 RAID Head - Manual (Page 615)

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Vess R2000 Series Product Manual Promise Technologies
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As it is used with Vess, the term cache refers to any of several kinds of high-speed, volatile memory that hold
data moving from your computer to the physical drives or vice-versa. Cache is important because it can read and
write data much faster than a physical drive. There are read caches, which hold data as it is read from a physical
drive; and write caches, which hold data as it is written to a physical drive.
In order to tune the cache for best performance in different applications, user-adjustable settings are provided.
Cache settings are made on the RAID controller. See “Making Controller Settings” on page 113.
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• Read Cache – The read cache is enabled but no pre-fetch action.
• Read Ahead – The read cache and predictive pre-fetch feature are enabled. Read-ahead anticipates the
next read and performs it before the request is made. Can increase read performance.
• Forced Read Ahead – The read cache and aggressive pre-fetch feature are enabled. See “Forced Read-
Ahead Cache” below.
• No Cache – The read cache is disabled.