[geeks] Cheap Dell Servers

[Shannon Hendrix]

On Feb 7, 2008, at 10:27 AM, nate at portents.com wrote:

>>> "One" is true except when using SATA port multipliers.  Then the
>>> answer
>>> becomes 15, though 15 is not a practical way to divide the bandwidth
>>> of a
>>> single SATA port.  The other stipulation is that the SATA host
>>> controller
>>> must support a SATA port multiplier.
>>
>> A SATA port multiplier is several ports combined into one.
>
> No, it's not:
>
> http://www.sata-io.org/portmultiplier.asp

Where does it say that this changes the 1:1 relationship between SATA  
port and SATA drive?

This just says a PM allows one physical port to carry several physical  
channels.

It looks to me like they still end up logically one drive per port.

I'm not saying you are wrong, but nothing you referenced says that  
this changes the 1:1 relationship, it just says a PM shares a single  
physical link with several physical ports.

If you look at 3Ware controllers, they use multi-lane cabling, where  
each drive gets full bandwidth.

That seems like a better solution, though I guess it is proprietary.

> No, as I said, there's a theoretical upward limit of 15, but in  
> practice
> they implement the port multipliers supporting 5 drives.

But isn't that just sharing a single link for the channels, but still  
connecting them 1:1 with their controller ports?

-- 
Shannon Hendrix
shannon at widomaker.com