NOTE: HP recommends using this option only with a 4 KiB sector size.
Values | Description |
| |
<list of serial | Indicates devices that need memory pre-allocated. A null |
numbers> | 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-formatcommand-line utility using the -boption. 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. |
General tuning techniques 19
