SAS3 SFF8643 "Link aggregation" ?

P

ponky

Limp Gawd
Joined
Nov 27, 2012
Messages
178
Just bought a Supermicro BPN-SAS3-846EL1 SAS3 backplane. I was reading the manual and noticed that the backplane has 4x SFF8643 connectors. Original SAS and SAS2 versions had 3x SFF8087 for 1 output to HBA and 2 for cascading.

I contacted Supermicro and they said that on 12Gbps backplanes two SFF8643 connectors can connect to one HBA for better bandwidth, but HBA / raid card has to support this. I could not find a name for this option.

Does anyone know what this "link aggregation" is called in HBAs / HW raids? It's not like I need it in my setup since I'm only running SATA3 HDDs, but it would be cool to know.
 
I am not sure what the official name is, but even the SAS2 version of the Supermicro backplane supports using two connections to the same HBA for double bandwidth. Supermicro doesn't officially support it in their documentation, but the chipset used in the SAS expander supports it and it works fine. On the SAS2 backplane, all ports are the same there is no difference between the HBA port and the 2 cascading ports other than labeling/location.

I suspect the SAS3 version is similar although I don't have any personal experience with it.

You didn't mention what chipset your HBA or RAID cards are using, but as long as your SAS3 HBA supports it, it should just work after the cables are connected. Most LSI SAS2 HBAs support multiple links so I would be surprised if most if not pretty much all of the LSI SAS3 HBAs do as well (also a lot of other brands use LSI chipsets and some are identical to certain LSI cards hardware/capability wise.)
 
wbo said:
I am not sure what the official name is, but even the SAS2 version of the Supermicro backplane supports using two connections to the same HBA for double bandwidth. Supermicro doesn't officially support it in their documentation, but the chipset used in the SAS expander supports it and it works fine. On the SAS2 backplane, all ports are the same there is no difference between the HBA port and the 2 cascading ports other than labeling/location.

I suspect the SAS3 version is similar although I don't have any personal experience with it.

You didn't mention what chipset your HBA or RAID cards are using, but as long as your SAS3 HBA supports it, it should just work after the cables are connected. Most LSI SAS2 HBAs support multiple links so I would be surprised if most if not pretty much all of the LSI SAS3 HBAs do as well (also a lot of other brands use LSI chipsets and some are identical to certain LSI cards hardware/capability wise.)
Click to expand...

Backplane uses LSI 3x36 or 3x24 expander and I'll be using a LSI 9300-series HBA. If all the ports work same way, why is there 4 ports instead of 3 like in SAS2 model? Can you connecto another backplane via dual cables to achieve double bandwidth in that situation as well?
 
If they don't document it, how will it auto sense which ports to use for aggregation? I have a Supermicro setup with the 2 SAS connectors coming from the m1015 and then from the backplane another connector going to the rear, 2nd backplane. The system sees both backplanes, but I haven't ever been able to get a connection which goes beyond a single backplane's max throughput of 768MB/s. The best I've seen, and this was a 9 disk array in RAID0, which pushed 752MB/s. I don't think I'm getting link aggregation...
 
ponky said:
Backplane uses LSI 3x36 or 3x24 expander and I'll be using a LSI 9300-series HBA. If all the ports work same way, why is there 4 ports instead of 3 like in SAS2 model? Can you connecto another backplane via dual cables to achieve double bandwidth in that situation as well?
Click to expand...

It is very possible that the backplane supports cascading with dual links to another enclosure/SAS expander. In fact, having dual links is often preferable when using multiple enclosures even in cases where the extra speed isn't necessary because it provides a degree of cable redundancy in the event an external SAS cable is accidently disconnected.

Your HBA almost certainly supports dual linking/link aggregation since it is based on the LSI SAS3008 chipset. I know the older LSI SAS2008 chipset supports dual linking and the 3008 appears to be the SAS 3 version of that.

With your expander you can connect two ports to your HBA and then you can either leave the other two ports unused or route them to a set of external connectors in the case for future expansion.
 
You must log in or register to reply here.
Back
Top