Switchover to CAM ATA?

[Andriy Gapon]

on 18/05/2010 18:09 Boris Kochergin said the following:
> Scott Long wrote:
>> On Apr 27, 2010, at 5:33 AM, Gavin Atkinson wrote:
>>
>>  
>>> On Mon, 2010-04-26 at 10:33 -0600, M. Warner Losh wrote:
>>>    
>>>> My opinion for the path forward:
>>>> (1) Send a big heads up about the future of ataraid(5).  It will be
>>>>    shot in the head soon, to be replaced be a bunch of geom classes
>>>>    for each different container format.  At least that seems to be
>>>>    the rough consensus I've seen so far.  We need worker bees to do
>>>>    many of these classes, although much can be mined from the ataraid
>>>>    code today.
>>>>       
>>> Losing ataraid would be bad.  I suspect there are a lot of installs
>>> using it - especially as there is no way to create any other mirror from
>>> sysinstall.  However, I'm not actually sure that the functionality it
>>> provides is easy to push down into GEOM.
>>>
>>> ataraid depends on knowing a lot about the underlying hardware, in order
>>> to know which format of metadata to use.  i.e. it needs to know that the
>>> disks are attached to (say) a Highpoint controller.
>>>     
>>
>> This is unfortunately true, especially on older controllers.  I think
>> that there
>> are reasonable ways to address this though, by having CAM SIMs provide a
>> bit more information in their PATH_INQ response.
>>
>> Scott
>>   
> I am thinking about trying to reimplement some ataraid stuff using GEOM
> as a summer programming exercise. Browsing the ataraid code, I notice
> that it tends to check both the PCI ID of the controller a disk is
> connected to, and a magic string identifying vendor-specific metadata
> belonging to the vendor of the controller. This leads me to believe that
> a lot of the pseudo-RAID formats can be used in GEOM without any
> knowledge of the controller type.

Just keep in mind the case when an HDD was used with a controller from one
vendor and then moved to a different system with a different controller.
So, pseudo-RAID label on disk may be different from actual pseudo-RAID hardware.

-- 
Andriy Gapon