Switching from MFI to MRSAS

[Tim Gustafson]

As I mentioned in my previous post last week, I have a new Dell R630
server that uses a Perc controller, and I have installed 4 SSD drives
and configured the PERC controller in pass-through mode.  However, the
PERC controller and its drives are being handled by the "mfi" driver,
which apparently does not support TRIM.

I have been reading up on all this, and I see that there is also an
"mrsas" driver that (according to the documentation) appears to be
compatible with my PERC controller, which is identified as follows:

mfi0: <Fury> port 0x2000-0x20ff mem
0x92000000-0x9200ffff,0x91f00000-0x91ffffff irq 26 at device 0.0 on
pci2
mfi0: Using MSI
mfi0: Megaraid SAS driver Ver 4.23
mfi0: FW MaxCmds = 240, limiting to 128
mfi0: MaxCmd = 240, Drv MaxCmd = 128, MaxSgl = 70, state = 0xb73c00f0

I see that there's a tunable for /boot/device.hints that I can set to
prefer mrsas over mfi:

hw.mfi.mrsas_enable="1"

and then add this to /boot/loader.conf:

mrsas_load="yes"

So, my question is: if I add those options and then reboot, will my
drives magically re-appear as /dev/da* devices?  Will the data on them
still be accessible as-is, or would I need to re-install the OS to get
this to go?  Would switching to this other driver enable the TRIM
command, as the devices will now be /dev/da* rather than
/dev/mfisyspd*?  Or am I just being naive here?  :)

-- 

Tim Gustafson
tjg at ucsc.edu
831-459-5354
Baskin Engineering, Room 313A