mfi driver performance too bad on LSI MegaRAID SAS 9260-8i

[Borja Marcos]

> On 22 Jun 2016, at 04:08, Jason Zhang <jasonzhang at cyphytech.com> wrote:
> 
> Mark,
> 
> Thanks
> 
> We have same RAID setting both on FreeBSD and CentOS including cache setting.  In FreeBSD, I enabled the write cache but the performance is the same.  
> 
> We don’t use ZFS or UFS, and test the performance on the RAW GEOM disk “mfidx” exported by mfi driver.  We observed the “gstat” result and found that the write latency
> is too high.  When we “dd" the disk with 8k, it is lower than 1ms, but it is 6ms on 64kb write.  It seems that each single write operation is very slow. But I don’t know
> whether it is a driver problem or not.

There is an option you can use (I do it all the time!) to make the card behave as a plain HBA so that the disks are handled by the “da” driver. 

Add this to /boot/loader.conf

hw.mfi.allow_cam_disk_passthrough=1
mfip_load=“YES"

And do the tests accessing the disks as “da”. To avoid confusions, it’s better to make sure the disks are not part of a “jbod” or logical volume configuration.




Borja.