Re: [dm-devel] [PATCH] fix default IO restrictions

[Mike Christie <mikenc us ibm com>]

Christophe Saout wrote:

> I don't think that will happen. The values are already the allowed
> maximum values. Or am I wrong?

I don't think they are the max values. SCSI will override them depending 
on the HBA settings.

Build a DM device from devices on a qla2300 or scsi_debug, and compare 
the request sizes and merges between accessing the DM device and 
accessing the SCSI device direclty.

> If the table isn't backed by a real device (like if it only contains an
> error target) the resulting queue will use those "unrealstic" values
> that exceed the system-wide limits. And a hardsect size of 0 bytes...

If you do not have a device, should you set sane IO restrictions in the 
target accroding to your target implementation limits.