LSI2008 and SAS3 backplane

[Andrew Vylegzhanin]

Hi!

I have a problem with low transfer speed (150MB/sec instead of 600Mb/sec)
on SAS2 controller to SAS3 drive via SAS3 backplane.

Hardware config is follows:

Dell R720 box with Dell SAS HBA 6Gbps connected with Supermicro 45-bay JBOD
with two SAS-3 expanders (LSI SAS3x40 and LSI SAS3x36). All drives (20 pcs)
are SEAGATE ST6000NM0095 E002.

So, partial dmesg out:
...
mps1: <Avago Technologies (LSI) SAS2008> port 0x9c00-0x9cff mem
0xd0ff0000-0xd0ffffff,0xd0f80000-0xd0fbffff irq 66 at device 0.0
numa-domain 1 on pci16
mps1: Firmware: 07.15.08.00, Driver: 21.02.00.00-fbsd
mps1: IOCCapabilities:
185c<ScsiTaskFull,DiagTrace,SnapBuf,EEDP,TransRetry,IR>
....
ses1 at mps1 bus 0 scbus8 target 81 lun 0
ses1: <LSI SAS3x40 0601> Fixed Enclosure Services SPC-3 SCSI device
ses1: 150.000MB/s transfers
ses1: Command Queueing enabled
ses1: SCSI-3 ENC Device
ses2 at mps1 bus 0 scbus8 target 82 lun 0
ses2: <LSI SAS3x36 0601> Fixed Enclosure Services SPC-3 SCSI device
ses2: 150.000MB/s transfers
ses2: Command Queueing enabled
ses2: SCSI-3 ENC Device
ses1: da0: Element descriptor: 'Slot00'
....
da0 at mps1 bus 0 scbus8 target 61 lun 0
da3 at mps1 bus 0 scbus8 target 64 lun 0
...
da0: <SEAGATE ST6000NM0095 E002> Fixed Direct Access SPC-4 SCSI device
da0: Serial Number ZAD119P20000C730KZK3
da0: 150.000MB/s transfers
da0: Command Queueing enabled
da0: 5723166MB (11721045168 512 byte sectors)

Some additional info.
There is two identical system with same problem.
System is under load now, and there is no erros, timeouts on disk i/o, so
it seems to be not cable/hardware problem.
I've tried other vendor SATA3 drive, got same 150MB/s.
This server works on full speed (600MB/s transfers) with SAS2 JBOD (Dell
MD1220)  w/o problems.

Any ideas?

--
Andrew