Switchover to CAM ATA?

[Boris Kochergin]

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. Sure, some CPU time would be wasted 
tasting all the supported formats in this manner, but it seems 
negligible given the frequency at which it would occur. I suppose there 
is also the unlikely chance that non-metadata information happens to 
live at the same location the metadata would, and the PCI ID check in 
the ataraid code is used to reduce that possibility, but it seems like 
additional sanity checking of RAID parameters following the magic string 
would alleviate this. Thoughts? Also, has there been any progress in 
making PCI ID information available to GEOM cleanly?

-Boris