john clyne wrote:
> Can anyone give me some guidance on where in the IO stack I might be running
> into a 512KB limit on IO transfer sizes to an external FC device? I've
> checked IO scheduler parameter
> (/sys/block/<dev>/queue/{max_sectors_kb,max_hw_sectors_kb}. Both are set to
> 32767. I'm using Qlogic HBAs (qla2312), but I don't see any relevent
> parameters. I'm running RHEL 4.0 with a 2.6.9-34 kernel. Any pointers would
> be greatly appreciated.
John,
I discuss the subject in this page:
http://www.torque.net/sg/sg_io.html
in the section titled:
Maximum transfer size per command
Mike C. has given you the answer for the block device
interface (e.g. via /dev/sda); you should be able
to do about 8 times better via the scsi generic
interface (e.g. /dev/sg0).
Doug Gilbert
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