raid1

[Chad Leigh -- Shire.Net LLC]

On Feb 18, 2005, at 11:56 PM, Josh Paetzel wrote:

> On Saturday 19 February 2005 00:51, Chad Leigh -- Shire.Net LLC wrote:
>> On Feb 18, 2005, at 11:39 PM, Spades wrote:
>>> hi, my server hardware supports hardware raid, i installed it
>>> as per normal freebsd 5.3, however i see no difference
>>> in df. its using 2 x 160GB, what do i do during the installation
>>> to enable the raid?
>>>
>>> mobo:
>>> http://www.supermicro.com/products/motherboard/Xeon800/E7320/X6DV
>>> L- EG.cfm
>>>
>>> -bash-2.05b$ df
>>> Filesystem  1K-blocks   Used    Avail Capacity  Mounted on
>>> /dev/ad4s1a  66008394  35424 60692300     0%    /
>>> devfs               1      1        0   100%    /dev
>>> /dev/ad4s1d  66008394     24 60727700     0%    /home
>>> /dev/ad4s1e  10154158 683442  8658384     7%    /usr
>>> /dev/ad4s1f   8172302    982  7517536     0%    /var
>>> -bash-2.05b$
>>
>> What do you expect to see?
>>
>> A raid1 is a mirror set and to the OS would probably look like a
>> single drive if it truly is a HW raid
>>
>> Chad
>
> The RAID will ususally show up as something other than ad(x).
> Generally you create the RAID array in the controller's BIOS and
> FreeBSD detects it as a single disk (in my case ar0).  You may want
> to google around to see if your controller is supported.

That is generally because they are not real HW raids, AFAIK.  My 
adaptec HW raid controller shows the raid arrays as daX just like a 
normal adaptec SCSI drive.  No difference.  (or my other adaptec ones 
show the raidsets and single drives as aacX, and my Rocket RAID 1820a 
seems to show everything as a daX)

I won't claim to know how this really works with these pseudo HW raid 
controllers built into the MBs, but from what I read in this list, 
FreeBSD has to read the RAID config on the disks in the ata driver, 
which to  me says it is not a real HW raid.  If it was a true HW raid, 
FreeBSD wouldn't be able to tell the difference between a raidset and a 
single disk.

Chad