Re: how to enlarge value of max_sectors_kb

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Tang,

> There is a machine with very little max_sectors_kb size:
> [root@ceph151 queue]# pwd
> /sys/block/sdd/queue
> [root@ceph151 queue]# cat max_hw_sectors_kb 
> 256
> [root@ceph151 queue]# cat max_sectors_kb 
> 256
>
> The performance is very low when I run big I/Os.
> I can not modify it directly, I need a little bigger,
> so how can I enlarge it?

max_hw_sectors_kb is set based on the DMA transfer capabilities of the
SCSI controller.

max_sectors_kb is a soft limit for regular filesystem I/O. It can not
exceed max_hw_sectors_kb since that would violate the hardware
constraints.

You need to figure out why your controller is limiting the transfer
size.

-- 
Martin K. Petersen	Oracle Linux Engineering



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