HP IO Accelerator for BladeSystem c-Class Performance Tuning Manual do Utilizador descarregar pdf (Página 19)

General tuning techniques 19

NOTE: HP recommends using this option only with a 4 KiB sector size.

Values Description

<list of serial

numbers>

Indicates devices that need memory pre-allocated. A null

list disables the pre-allocation of memory.

preallocate_mb

Description

Specifies the number of megabytes of memory to pre-allocate. The sector size is set with the fio-format

command-line utility using the -b option. Larger sector sizes result in less memory utilization.

Values Description

0 (default)

Use the pre-allocate size calculator algorithm (do not

specify the size of pre-allocated memory).

<size, MB>

Disable the pre-allocate size calculator algorithm and

pre-allocate the amount of memory specified in MB.

expected_io_size

Description

This module parameter is useful when preallocate_memory is set through the Management Tool or a supplied

list of serial numbers and preallocate_mb is left at the default (0).

It overrides the value provided to the pre-allocate size calculator algorithm. The default is built to handle

worst-case memory utilization (which is the sector size of the device). For example, if your application writes

I/O blocks larger than the sector size (such as when the drive is formatted for 512 byte sectors, but the

application does 8 KiB I/O, then setting this parameter to 8192 when memory pre-allocation is enabled will

significantly reduce the amount of pre-allocated memory.

Values Description

0 (Default)

Don’t pre-allocate memory

<size, MB>

Allocate the specified amount of memory, in megabytes.

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HP IO Accelerator for BladeSystem c-Class Performance Tuning Manual do Utilizador Página 19