SAS Expander bottleneck?

[rkruz]

SAS states a throughput of 3 (or 6Gbps). So if an expander is used, ultimately all the drives on that layer are bottlenecked by the single 3Gbps SAS interface to the host controller?
I attempted to attach a simple block diagram to help illustrate.
thanks for any insight

 

[Handruin]

That's my understanding of it also. I asked a similar question in this thread related to the HP expander card. The suggestion was to run more than one cable from the expander to the SAS controller to reduce the bottleneck.

 

[LunarMist]

Well it is an expander. If you want top performance there are better controller options.

 

[MaxBurn]

Also the newer ones support the SATA6GB/SAS2 stuff. The HBA must as well obviously.

 

[rkruz]

Thanks. I just wanted to confirm my belief. Worse case is a SAS to each drive which is not bad since the controller Im looking at has 8.
thanks again

 

[Pradeep]

SAS expanders give large capacity possibilities via daisychaining, however as you have seen they provide limited bandwidth.