Switching from MFI to MRSAS

[Tim Gustafson]

> The mrsas driver is interesting.  Your RAID volumes show up as da0, da1,
> etc, but they really shouldn't.  I'm doubtful that TRIM will work here
> because the drives are not truly directly attached, even though the mrsas
> driver is misleading the kernel into thinking that they are.
>
> You can always give a try, though.

Just to be clear: we have the PERC controller configured in
"pass-through" mode, which I understand to mean "HBA" mode.  We are
not using any of the RAID features of the PERC card.  Instead, the
server is configured as ZFS-on-root in a RAID 0+1 configuration:

  pool: tank
 state: ONLINE
  scan: scrub repaired 14.5K in 0h13m with 0 errors on Thu Sep 17 20:47:17 2015
config:

NAME             STATE     READ WRITE CKSUM
tank           ONLINE       0     0     0
 mirror-0       ONLINE       0     0     0
   mfisyspd0p3  ONLINE       0     0     0
   mfisyspd1p3  ONLINE       0     0     0
 mirror-1       ONLINE       0     0     0
   mfisyspd3p3  ONLINE       0     0     0
   mfisyspd2p3  ONLINE       0     0     0

where mfisyspd0, mfisyspd1, mfisyspd2 and mfisyspd3 are Samsung SSDs,
not RAID volumes.

So in this case, I believe it would be "correct" for the RAID
controller to report the devices as "da0", "da1" and so on.

-- 

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