Re: Are SATA port multipliers supported in -CURRENT?

Barry Pederson wrote:
> Martin Nilsson wrote:
>> Hi,
>>
>> Have you looked at the Supermicro CSE-836E1 chassis?
>> http://www.supermicro.com/products/chassis/3U/836/SC836E1-R800V.cfm
>>
>> It is also 3U but have space for 16 drives redundant power and the 
>> computer! The port expander works with the LSI MegaRAID SAS8308ELP 
>> board and SAS/SATA drives in FreeBSD. There is also a cheaper model 
>> available with 16 normal SATA connectors if you prefer that.
> 
> I've been pondering this chassis too, and have been wondering how the 
> FreeBSD mpt driver would react to the builtin SAS expander.  I've been 
> using SAS3041E-R cards (cheaper than the MegaRAIDs) with drives plugged 
> straight into them very happily.  Would that same 4-port card plugged 
> into a that chassis' expander simply see 16 sata drives as da0..da15?
> 
> It looks like these chassis actually have 28-port expanders, with 4 
> ports going in, 16 ports for drives, and 2 4-port groups for 
> daisy-chaining other chassis.  Any idea if another connected chassis 
> full of drives would just show up as da16..da31 and so on?
> 

There are two possible scenarios here, first is that the controller does
a full topology scan and presents the drives to the OS with no OS
intervention.  Second is that it doesn't do a full scan, and instead
presents only the drives that are directly attached.  Given that the
Linux driver does full discovery itself, I kind of suspect that the
latter behavior is what will happen.

Full SAS support is on my immediate TODO list, but it's a fairly big
project.

Scott