MRSAS(4) FreeBSD Kernel Interfaces Manual MRSAS(4)


mrsasLSI MegaRAID 6Gb/s and 12Gb/s SAS+SATA RAID controller driver


To compile this driver into the kernel, place the following lines in your kernel configuration file:

device pci
device mrsas

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):



The mrsas driver will detect LSI's next generation (6Gb/s and 12Gb/s) PCI Express SAS/SATA RAID controllers. See the HARDWARE section for the supported devices list. A disk (virtual disk/physical disk) attached to the mrsas driver will be visible to the user through camcontrol(8) as /dev/da? device nodes. A simple management interface is also provided on a per-controller basis via the /dev/mrsas? device node.

The mrsas name is derived from the phrase "MegaRAID SAS HBA", which is substantially different than the old "MegaRAID" Driver mfi(4) which does not connect targets to the cam(4) layer and thus requires a new driver which attaches targets to the cam(4) layer. Older MegaRAID controllers are supported by mfi(4) and will not work with mrsas, but both the mfi(4) and mrsas drivers can detect and manage the LSI MegaRAID SAS 2208/2308/3008/3108 series of controllers.

The device.hints(5) option is provided to tune the mrsas driver's behavior for LSI MegaRAID SAS 2208/2308/3008/3108 controllers. By default, the mfi(4) driver will detect these controllers. See the PRIORITY section to know more about driver priority for MR-Fusion devices.

mrsas will provide a priority of (-30) (between BUS_PROBE_DEFAULT and BUS_PROBE_LOW_PRIORITY) at probe call for device id's 0x005B, 0x005D, and 0x005F so that mrsas does not take control of these devices without user intervention.


The mrsas driver supports the following hardware:

[ Thunderbolt 6Gb/s MR controller ]

  • LSI MegaRAID SAS 9265
  • LSI MegaRAID SAS 9266
  • LSI MegaRAID SAS 9267
  • LSI MegaRAID SAS 9270
  • LSI MegaRAID SAS 9271
  • LSI MegaRAID SAS 9272
  • LSI MegaRAID SAS 9285
  • LSI MegaRAID SAS 9286
  • DELL PERC H810
  • DELL PERC H710/P

[ Invader/Fury 12Gb/s MR controller ]

  • LSI MegaRAID SAS 9380
  • LSI MegaRAID SAS 9361
  • LSI MegaRAID SAS 9341
  • DELL PERC H830
  • DELL PERC H730/P
  • DELL PERC H330


To disable Online Controller Reset(OCR) for a specific mrsas driver instance, set the following tunable value in loader.conf(5):


where X is the adapter number.

To change the I/O timeout value for a specific mrsas driver instance, set the following tunable value in loader.conf(5):


where NNNNNN is the timeout value in milli-seconds.

To change the firmware fault check timer value for a specific mrsas driver instance, set the following tunable value in loader.conf(5):


where NN is the fault check delay value in seconds.

The current number of active I/O commands is shown in the dev.mrsas.X.fw_outstanding sysctl(8) variable.


To enable debugging prints from the mrsas driver, set the hw.mrsas.X.debug_level variable, where X is the adapter number, either in loader.conf(5) or via sysctl(8). The following bits have the described effects:
Enable informational prints.
Enable tracing prints.
Enable prints for driver faults.
Enable prints for OCR and I/O timeout.
Enable prints for AEN events.


The mrsas driver will always set a default (-30) priority in the PCI subsystem for selection of MR-Fusion cards. (It is between BUS_PROBE_DEFAULT and BUS_PROBE_LOW_PRIORITY). MR-Fusion Controllers include all cards with the Device IDs - 0x005B, 0x005D, 0x005F.

The mfi(4) driver will set a priority of either BUS_PROBE_DEFAULT or BUS_PROBE_LOW_PRIORITY (depending on the device.hints setting) in the PCI subsystem for selection of MR-Fusion cards. With the above design in place, the mfi(4) driver will attach to a MR-Fusion card given that it has a higher priority than mrsas.

Using /boot/device.hints (as mentioned below), the user can provide a preference for the mrsas driver to detect a MR-Fusion card instead of the mfi(4) driver.


At boot time, the mfi(4) driver will get priority to detect MR-Fusion controllers by default. Before changing this default driver selection policy, LSI advises users to understand how the driver selection policy works. LSI's policy is to provide priority to the mfi(4) driver to detect MR-Fusion cards, but allow for the ability to choose the mrsas driver to detect MR-Fusion cards.

LSI recommends setting hw.mfi.mrsas_enable="0" for customers who are using the older mfi(4) driver and do not want to switch to mrsas. For those customers who are using a MR-Fusion controller for the first time, LSI recommends using the mrsas driver and setting hw.mfi.mrsas_enable="1".

Changing the default behavior is well tested under most conditions, but unexpected behavior may pop up if more complex and unrealistic operations are executed by switching between the mfi(4) and mrsas drivers for MR-Fusion. Switching drivers is designed to happen only one time. Although multiple switching is possible, it is not recommended. The user should decide from Start of Day which driver they want to use for the MR-Fusion card.

The user may see different device names when switching from mfi(4) to mrsas. This behavior is Functions As Designed and the user needs to change the fstab(5) entry manually if they are doing any experiments with mfi(4) and mrsas interoperability.


array/logical disk interface
management interface


The mrsas driver first appeared in FreeBSD 10.1.

mfi Driver: mfi(4) is the old FreeBSD driver which started with support for Gen-1 Controllers and was extended to support up to MR-Fusion (Device ID = 0x005B, 0x005D, 0x005F).

mrsas Driver: mrsas is the new driver reworked by LSI which supports Thunderbolt and onward products. The SAS+SATA RAID controller with device id 0x005b is referred to as the Thunderbolt controller throughout this man page.

cam aware HBA drivers: FreeBSD has a cam(4) layer which attaches storage devices and provides a common access mechanism to storage controllers and attached devices. The mrsas driver is cam(4) aware and devices associated with mrsas can be seen using camcontrol(8). The mfi(4) driver does not understand the cam(4) layer and it directly associates storage disks to the block layer.

Thunderbolt Controller: This is the 6Gb/s MegaRAID HBA card which has device id 0x005B.

Invader Controller: This is 12Gb/s MegaRAID HBA card which has device id 0x005D.

Fury Controller: This is the 12Gb/s MegaRAID HBA card which has device id 0x005F.


The mrsas driver and this manual page were written by Kashyap Desai <Kashyap.Desai@lsi.com>.


The driver does not support big-endian architectures at this time.

The driver does not support alias for device name (it is required when the user switches between two drivers and does not want to edit /etc/fstab manually).

The mrsas driver exposes devices as /dev/da?, whereas mfi(4) exposes devices as /dev/mfid?.

mrsas does not support the Linux Emulator interface.

mrsas will not work with mfiutil(8).

May 8, 2014 FreeBSD