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Technology Background
Pegasus3 Product Manual
RAID Controllers
RAID controller technology includes:
•
Cache Policy (“Read Cache Policy” and “Write Cache Policy”)
•
As it is used with Pegasus, 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
25.
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.
No Cache
– The read cache is disabled.
Write Cache Policy
Write Back
– Data is written first to the cache, then to the logical drive.
This provides better performance.
Write Thru
– Also “Write Through.” Data is written to the cache and the logical drive at the same
time. This is safer.
Summary of Contents for Pegasus3 R4
Page 4: ...iv Promise Technology Pegasus3 R4 R6 R8 VCCI KCC FCC ...
Page 5: ...v About this guide Pegasus3 Product Manual WARNING WARNING WARNING WARNING ...
Page 80: ...67 Managing the Pegasus3 Pegasus3 Product Manual Controller Settings ...
Page 207: ...194 Promise Technology Pegasus3 R4 R6 R8 View NVRAM Events ...