User manual

SuperTrak EX Series User Manual
246
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 – Continues reading ahead even when the next read
cannot be logically anticipated. 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.
Better performance. Requires a cache backup battery to protect data in the
cache from a sudden power failure.
• Write Through – Data is written to the cache and the logical drive at the
same time. Safer.
• Adaptive Writeback Cache – Data is written first to the cache, then to the
logical drive. Changes the write cache settings while the cache backup
battery is offline.
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
The write policy automatically changes to Write Through. When the battery
comes back online, the write policy automatically changes back to Write
Back.
Capacity Coercion
This feature is designed for fault-tolerant logical drives (RAID 1, 1E, 5, 6, 10, 50,
and 60). It is generally recommended to use physical drives of the same size in
your disk arrays. When this is not possible, physical drives of different sizes will
work but the system must adjust for the size differences by reducing or coercing
the capacity of the larger drives to match the smaller ones. With SuperTrak, you
can choose to enable Capacity Coercion and any one of four methods.
Enable Capacity Coercion and choose the Method in the Controller Settings
menu. See “Making Controller Settings” on page 144. The choices are:
• GBTruncate – (Default) Reduces the useful capacity to the nearest
1,000,000,000-byte boundary.