mrsas/mfi : is /dev/megaraid_sas_ioctl_node just a proxy?

[Dan Langille]

Hello,

I'm working with the same hosts Wallace recently mentioned[1] but we one remaining question.

It seem that the the PERC H730P Mini (Embedded) SCSI card can present different devices
depending upon the driver. We have the card in HBA mode. pciconf -lv shows chip 0x005d100.
man mrsas shows this is the Invader Controller.

Our question is about a the /dev/megaraid_sas_ioctl_node symlink which seems to just point
to the real driver. i.e. the symlink is a proxy

If we put this in /boot/loader.conf:

   hw.mfi.mrsas_enable="1"

The symlink looks like:

$ ls -l /dev/megaraid_sas_ioctl_node
lrwxr-xr-x  1 root  wheel  6 Sep 17 18:34 /dev/megaraid_sas_ioctl_node -> mrsas0

This gives us da0 and da1 ... which is what we would expect (and want) based on the
man page.

If we don't enable mrsas, we get this:

$ ls -l /dev/megaraid_sas_ioctl_node
lrwxr-xr-x  1 root  wheel  4 Aug 23 19:25 /dev/megaraid_sas_ioctl_node -> mfi0

Instead of da0/da1, we get mfisyspd0 & mfisyspd1

Is the symlink how the different drivers are invoked?

We think we should use mrsas because it gives us the expected devices. We are mostly
looking for wanted confirmation that we are not planting a long-term problem. 


Thank you

-- 
  Dan Langille
  dan at langille.org


[1] - https://lists.freebsd.org/pipermail/freebsd-scsi/2019-September/008028.html