User Manual

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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.
reAd cAche POlicy
• 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.