Read Cache Policy; Write Cache Policy; Forced Read-Ahead Cache; Adaptive Writeback Cache - Promise Technology 1000f series Product Manual
Fc, iscsi, sas external disk array subsystems
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Also See for 1000f series:
- Product manual (28 pages) ,
- Product manual (438 pages) ,
- Quick start manual (472 pages)
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VessRAID 1000f, 1000i, 1000s Product Manual
Read Cache Policy
•
Read Cache – The read cache is enabled.
•
Read Ahead – The read cache and the read-ahead 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.
Write Cache Policy
•
Write Back – Data is written first to the cache, then to the logical drive.
Better performance. VessRAID has a cache backup battery to protect data in
the cache from a sudden power failure.
•
Write Thru – Also "Write Through". Data is written to the cache and the
logical drive at the same time. Safer.
If your write cache policy is set to Write Back, the write policy automatically
changes to Write Thru when all of the following conditions occur:
•
The logical drive write policy is set to Write Back
•
The Adaptive Writeback Cache feature is enabled
•
The cache backup battery goes offline
When the battery comes back online, the write policy automatically changes back
to Write Back.
Forced Read-Ahead Cache
On the VessRAID subsystem, you can set the logical drive read cache policy to
Forced Read Ahead an enable the aggressive pre-fetch feature.
The Forced Read-Ahead cache policy setting provides predictive pre-fetching of
data requests, allowing the controller to aggressively buffer large chunks of data
in cache memory to prevent frame drops on high-bandwidth video playback. Not
normally enabled for non-video applications.
Adaptive Writeback Cache
On the VessRAID subsystem, you can set the logical drive write cache policy to
Write Thru or Write Back.
If you set the write cache policy to Write Back, your data is first written to the
controller cache, and later to the logical drive. This action improves performance.
To preserve the data in the cache in the event of a power failure, the subsystem
has a backup battery that powers the cache. To see an estimate of how long the
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