Acer SmartRAID V Bedienungsanleitung PDF herunterladen (Seite 158)

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Storage Manager

I/O Commands

The number of read and write commands issued

by the computer to the controller. If you use RAID

and caching, the number of commands issued to

the drives can differ significantly from this value.

Total S ectors

The total number of sectors read and written

from the host computer.

Cache Hits

The total number of sectors (read or written from

the host computer) that were found in the

controller cache and did not require a disk access.

Read-Ahead Hits

The number of the cache hits for data read

requests satisfied by data held in the cache from

previous disk read-ahead operations.

Write-Backs

The number of sectors written to disk that were

held in the controller cache and written some

time after the host write command reported as

completed.

Write-Throughs

The number of sectors written directly to disk

before the write command ended.

In RAID 1 arrays, (Write-Backs + Write-Throughs) can be up to twice the

value of Total Sectors because each sector written from the host results in

a write to each mirrored disk. In RAID 5 arrays, each write from the host

can generate up to two disk reads and two disk writes. If the controller has

cache memory, this can result in the actual number of sectors read from

or written to disk being reported as less than this value.

Environments with a large number of sequential reads should generate a

high number of Read-Ahead Hits relative to Total Sectors. These hits

reduce the number of seek operations and increase performance. The

read-ahead hits count can be increased by adding more cache memory to

the controller. A high percentage of 4KB or smaller I/O operations also

indicates that increasing the controller cache would be beneficial.

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Acer SmartRAID V Bedienungsanleitung Seite 158