IBM Netfinity ServeRAID-3H, Инструкция по установке и эксплуатации, Страница: 55 / 212

This choice
does not change any of the ServeRAID
adapter or controller settings (such as the stripe-unit
size, rebuild rate, and so on) from their current or
customized values.
Ÿ
Copy the Configuration from the Drives to the
Controller: This choice is available in the Information
mode only; it copies the configuration information
stored on the hard disk drives to the ServeRAID
controller. This function is useful when you import
previously configured drives from another system, or
when you replace the ServeRAID adapter or controller.
Ÿ
Disable or Enable Read-Ahead Cache Mode: These
choices are available in the Information mode only.
When read-ahead cache is set to Enabled (default
setting), the ServeRAID controller transfers data from a
disk to its local cache in increments equal to the
stripe-unit size. This provides excellent overall
performance when workloads are steady and
sequential. However, if the workload is random or the
system I/O requests are smaller than the stripe-unit
size, reading ahead to the end of the stripe might
degrade performance. When read-ahead cache is set
to Disabled, the ServeRAID controller transfers data
from a disk to local cache in increments equal to the
system I/O request size, without reading ahead to the
end of the stripe.
Ÿ
Change the Rebuild Rate: This choice is available in
the Information mode only. You can select this choice
to set the priority for Rebuild operations to High
(default), Medium, or Low.
– When the rebuild rate is set to High, the rebuild I/O
request gets high priority in the execution order.
– When the rebuild request is set from High to
Medium in a heavily loaded system, it can increase
the rebuild time, but provide better system
performance.
Chapter 3. Using the Configuration Programs
45