3ware driver maximum request size

Does anyone know why the 3ware driver caps I/O at 128K bytes per scsi request? The driver defines a scatter gather array which will always cope with at least twice this.

I am running with the TW_MAX_SECTORS constant at 512 and getting 256K I/Os to a 6+1 raid5 lun on a 9550SX. By my calculations this does not exceed the defined sizes of the scatter gather arrays for this type of device (but would I guess for the escalade variant in the code).

I know nothing about the hardware itself, but if this works it seems like a worthwhile change for the newer devices.

Thanks

Steve Lord

Steve,

It's capped at 128k per request because that is the max size the firmware was tested with. If you increase that number, it is at your own risk, and you may have problems.

-Adam

Thanks Adam,

It does seem capable of handling it under basic testing, guess I will take that under advisement. So far the perf difference is not that large, so maybe it is best left alone.

Steve