SATA mirrror performance

[Joao Carlos Mendes Luis]

Ashley Moran wrote:
>
> On Sep 17, 2007, at 2:52 am, João Carlos Mendes Luís wrote:
>
>>    After using gmirror, now I have the RAID in its full performance,
>> getting over 60Mbytes per second at raw reads, very near the 70MBps from
>> the specs.  Could only be better if we already had NCQ working.
>>
>>    Now the question: Is this expected?  Is ataraid somehow deprecated?
>
> I had no end of trouble with ataraid.  At first I was under the 
> impression it was the best solution, seeing as it has some support 
> from the motherboard.  But after posting to a list (possibly 
> -hardware) a long time ago, all the answers I got were to use 
> gmirror.  I don't know that ataraid is deprecated, but I can't think 
> of any reason to use it.  Fortunately (as you have found), turning an 
> ataraid mirror into a gmirror is easy.  I would just use gmirror and 
> not worry about it.

The main advantage of ataraid is its integration with BIOS and other 
operating systems.  If we had something like a master GEOM device which 
could read ata raid specs and build GEOM graphs based on this 
information, that would be a good workaround.  I am not sure if this is 
enough, but at least would solve startup problems.  I am also not sure 
if it is even possible, because no single GEOM device would suffice: The 
master device should recognize disk labels, and call geom_mirror, 
geom_strip, geom_raid5, etc when needed.  I hope GEOM architects have 
something in mind, because this is very important to desktop and dual boot.

I can deal with geom_mirror, but I am not a typical user.  Most users 
don't even know FreeBSD supports mirroring, since it is not on 
installation options menu.  Indeed, install a FreeBSD with boot mirror 
support was still a complex task the last time I saw sysinstall.

Thanks for your info, anyway...