# LSI2008 HBAs and JBOD mode with SATA disks



## AndyUKG (Aug 25, 2011)

Hi,

  I am looking to replace some eSATA connected storage with something (mini)SAS connected. But I'm asking myself how does this actually work. The LSI2008 based cards seem a good option, how does the MPT driver handle SATA disks, does it effectively switch to SATA mode when it sees SATA disks or do the SAS enclosures do some sort of translation (which seems unlikely).
Also on another point, are JBOD mode LSI2008 cards available to buy or do you always have to do this thing of flashing the BIOS (and I suppose ending up with an unsupported HBA)?

thanks for any info,

Andy.

PS would seem the driver is mps not mpt2 for these LSI cards.


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## AndyUKG (Aug 25, 2011)

Ok, answer to how does a SAS HBA communicate to SATA devices is explained here:

http://en.wikipedia.org/wiki/Serial_attached_SCSI



> SAS controllers may support connecting to SATA devices, either directly connected using native SATA protocol or through SAS expanders using SATA Tunneled Protocol (STP).



I assume both of these methods are supported in the mps driver, can anyone confirm?

thanks Andy.


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## phoenix (Aug 25, 2011)

It all depends on the backplane (or cables) you select.

Those cards speak both SAS and SATA protocols.

So, if you get break-out cables (mini-SAS on one end, multiple SATA on the other) then you can directly connect SATA drives to the card.  Or, you can connect to a direct-attached SATA backplane (where there's individual SATA ports on the backside of the backplane) -- these are what we are using currently.

Or, you can get mini-SAS cables (SFF-8087 connectors on both ends) and connect them to a SATA backplane (each cable supports 4x SATA channels).  You still get a 1:1 SATA drive to SATA port to SATA channel ratio, but you save cabling.

Or, you can get mini-SAS cables (SFF-8087 on both ends) and connect them to a SAS/SATA backplane.  Same setup as above, but gives you the option of upgrading down the road to SAS drives.  Still a 1:1 drive/port/channel ratio.

And then you can get SATA Port Multipliers, and connect the controller to those via mini-SAS.  This is where you start overloading the SATA channels:  a standard cable will connect 4 SATA channels to the port multipler, which will generally allow you to connect 12 or 16 SATA drives (3 or 4 drives per channel).

And, finally, you can get SAS Expanders, but that requires SAS drives as you cannot use SATA drives in a SAS Expander, since the Expanders only support the SAS protocol.

We just went through this whole rigamarole with our latest storage server using a SuperMicro SC836 chassis.  We requested support for SATA ... and they sent us the SC836EL1 backplane (SAS Expander).  Now we're trying to get it returned and replaced with the SC836A backplane (SATA backplane with SFF-8087 connectors so only 3 cables needed for 12 drives), or even the SC836TQ backplane (SATA backplane with 12x SATA connectors on the back).


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## AndyUKG (Aug 26, 2011)

Hi Phoenix,

  thanks for the info. Interesting what you say about SAS expanders, in wikipedia it says that SATA devices can be connected via SAS expanders whereby the SAS expander will communicate over STP to the SAS HBA. Perhaps this isn't implemented in the drivers in FreeBSD yet??
I had been imagining going the SAS expander route, as a preferred option to SATA PMs for having multiple disks per SAS/SATA bus,

thanks Andy.


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## olav (Aug 26, 2011)

It is cheaper to just get 3 SAS2008 controllers, it will be faster too. SAS expanders really shine when you need a 256+ disk setup with jbod nodes. But to have a reliable setup you need SAS drives.


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## AndyUKG (Aug 26, 2011)

olav said:
			
		

> It is cheaper to just get 3 SAS2008 controllers, it will be faster too. SAS expanders really shine when you need a 256+ disk setup with jbod nodes. But to have a reliable setup you need SAS drives.



I'd like to be able to connect a large number of disks without millions of cables and PCI cards, we have been using SATA PM disk shelves.
I am seeing a few reports of poor reliability of SAS expanders with SATA disks, but on (open)Solaris. Anyone aware of any stories of how stable this is on FreeBSD?

thanks Andy.


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## Crivens (Aug 26, 2011)

phoenix said:
			
		

> It all depends on the backplane (or cables) you select.
> 
> Those cards speak both SAS and SATA protocols.
> 
> So, if you get break-out cables (mini-SAS on one end, multiple SATA on the other) then you can directly connect SATA drives to the card ....


Anyone has experience with such cables? I do face a similar challenge and would like to connect 8 discs to two SAS ports (Adaptec 1405 would be my option here).


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## olav (Aug 26, 2011)

They work just like sata cables. Though make sure you get forward and not reverse breakout cables.


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## phoenix (Aug 29, 2011)

AndyUKG said:
			
		

> thanks for the info. Interesting what you say about SAS expanders, in wikipedia it says that SATA devices can be connected via SAS expanders whereby the SAS expander will communicate over STP to the SAS HBA. Perhaps this isn't implemented in the drivers in FreeBSD yet??



I'm going by the documentation that comes with the SuperMicro SC836EL1 chassis, which uses SAS expander backplanes.  Or maybe just SAS backplanes?  Either way, it only supports SAS drives, no SATA allowed.


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## phoenix (Aug 29, 2011)

Crivens said:
			
		

> Anyone has experience with such cables? I do face a similar challenge and would like to connect 8 discs to two SAS ports (Adaptec 1405 would be my option here).



We use those in all our servers.

The Linux servers have 3Ware 9550SXU and 9650SE RAID controllers directly connected to SATA drives via the SFF-8087 breakout cables.  Mini-SAS (SFF-8087) connector on one end, 4x standard SATA connectors on the other end.

The FreeBSD servers have SuperMicro AOC-USAS-L8i controllers connected to direct-connect SATA backplanes, using the same cables as above.

Some cables are from 3Ware, some cables are from SuperMicro, some cables are generic.  They all work with all the controllers.


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## AndyUKG (Aug 30, 2011)

phoenix said:
			
		

> I'm going by the documentation that comes with the SuperMicro SC836EL1 chassis, which uses SAS expander backplanes.  Or maybe just SAS backplanes?  Either way, it only supports SAS drives, no SATA allowed.



Fair enough, that sounds like just a limitation of that particular product. To support SATA it not only needs to be able to handle the tunneling but it needs the physical SATA connectors which it would seem logical isn't offered in every product...

thanks Andy.


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## AndyUKG (Aug 30, 2011)

phoenix said:
			
		

> The Linux servers have 3Ware 9550SXU and 9650SE RAID controllers directly connected to SATA drives via the SFF-8087 breakout cables.  Mini-SAS (SFF-8087) connector on one end, 4x standard SATA connectors on the other end.
> 
> The FreeBSD servers have SuperMicro AOC-USAS-L8i controllers connected to direct-connect SATA backplanes, using the same cables as above.



Are those connected to internal disks or external shelves? If external would you mind sharing what product you use?

thanks Andy.


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## aragon (Aug 30, 2011)

phoenix said:
			
		

> The FreeBSD servers have SuperMicro AOC-USAS-L8i controllers connected to direct-connect SATA backplanes, using the same cables as above.


Same here but with SuperMicro's USAS2 controllers, and these cables.

Disks connected internally, directly...


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