Hardware Raid on Intel DG965OT Motherboard

Antony Mawer fbsd-questions at mawer.org
Thu Apr 12 03:29:52 UTC 2007

On 5/04/2007 1:52 AM, Alexander Anderson wrote:
> Thu, Apr 05, 2007 at 08:52:44 AM, Antony Mawer wrote:
>>> I have Intel D975XBX2 with two on-board SATA RAID controllers: one is Intel
>>> Matrix and the other is Marvell storage. I have FreeBSD 6.2 with RAID-5
>>> using Intel Matrix Storage. It seems to work fine.
>> You may want to re-think that option... according to the ataraid(4) man 
>> page, RAID5 is not functional (ie. you have about as much data safety as 
>> a RAID0 stripe set does):
>>>     RAID5 is not supported at this time.  Code exists, but it neither uses
>>>     nor maintains parity information.
> The ataraid driver provides *software* RAID. But doesn't Intel Matrix
> Storage gives *hardware* RAID support? How could I tell if software is at
> play?

I'm fairly certain that all ar# devices (ar0, etc) are ataraid-powered, 
and thus are software RAID. If it is a hardware RAID device, typically 
the RAID controller presents a single drive (or one drive for each RAID 
volume) to the OS, and the OS can be ignorant of the number of 
underlying drives.

Also, from man ataraid:

      The ataraid driver can read the following metadata formats:

      o   Intel MatrixRAID

Which suggests that is is, indeed, just a software RAID setup. That is, 
the BIOS-based bit just writes configuration metadata to the drives, and 
  its up to drivers at the OS level to perform the actual RAID 
operations using that data.


More information about the freebsd-questions mailing list