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Re: FIXED: mpt Serious performance issues

On Fri, 4 Feb 2011, Thor Lancelot Simon wrote:

> If the firmware vendor did *not* get it wrong, then there is a separate
> page which holds these settings for the "logical" disk, and when we are
> operating in RAID mode we need to use that one instead of ever accessing
> the 16 pages for the physical disks.  Do you have enough documentation
> to say if it actually works this way?

ISTR MPI is nasty in this regard.  When it generates a RAID volume it uses 
one "target ID" which may or may not be the one used by the first physical 
disk of the RAID volume.  If it is, then the RAID volume replaces the 
first disk, but other disks that are part of the volume are still visible.  
If you're operating in mixed mode, with some RAID volumes and some disks 
being accessed directly things get really confusing.  LSI may have finally 
fixed this in newer firmware.

To do this properly, the driver should probe the controller (I'm not 
saying "bus" here since it's not really a SCSI bus but a firmware 
generated simulation of a SCSI bus) and identify all RAID volumes, then 
query each volume for its constituent disks and block access to them.


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