Promise Technology M200f, M500i, M500f manual Capacity Coercion, Write Cache Policy, Cache Line Size

VTrak M-Class Product Manual

•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.

•No Cache – The read cache is disabled.

Write Cache Policy

•Write Back – Data is written first to the cache, then to the physical drive. Better performance. VTrak 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 physical drive at the same time. Safer.

Cache Line Size

The cache line size refers to the size of data the controller handles internally during a data input/output (I/O) operation.

•8KB – Increases the number of I/O operations. Use this setting if your I/O operations are low-bandwidth (512B to 8KB).

•64KB – Decreases the number of I/O operations. Use this setting if your I/O operations are high-bandwidth (64KB to 1MB).

If your I/O operations vary or they fall into the mid-bandwidth range (8KB to 64KB), use either setting.

Capacity Coercion

This feature is designed for fault-tolerant logical drives (RAID 1, 1E, 5, 10, and 50). 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 VTrak, you can choose to enable Capacity Coercion and any one of four methods.

Enable Capacity Coercion and select the Method in the Controller Settings menu. The choices are:

•GB Truncate – (Default) Reduces the useful capacity to the nearest 1,000,000,000 byte boundary.

•10GB Truncate – Reduces the useful capacity to the nearest 10,000,000,000 byte boundary.

•Group Rounding – Uses an algorithm to determine how much to truncate. Results in the maximum amount of usable drive capacity.

•Table Rounding – Applies a predefined table to determine how much to truncate.

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