Unable to connect to Dell MD-3000 disk array

Issue

• Unable to connect to Dell MD-3000 disk array
• When attach Dell MD-3000 disk array to a RHEL 6.2 host via SAS inteface, only generic scsi devices (/dev/sg) are created but no block devices are attached - see the kernel log:

Jun 13 17:41:09 hostname kernel: mptsas: ioc0: attaching ssp device: fw_channel 0, fw_id 0, phy 0, sas_addr 0x5001ec94f207a404
Jun 13 17:41:09 hostname kernel: scsi 4:0:0:0: Direct-Access     DELL     MD3000           0735 PQ: 1 ANSI: 5
Jun 13 17:41:09 hostname kernel: scsi 4:0:0:0: Attached scsi generic sg6 type 0
Jun 13 17:41:09 hostname kernel: scsi 4:0:0:0: Embedded Enclosure Device
Jun 13 17:41:09 hostname kernel: scsi 4:0:0:0: Failed to get diagnostic page 0x8000002
Jun 13 17:41:09 hostname kernel: scsi 4:0:0:0: Failed to bind enclosure -19
Jun 13 17:41:09 hostname kernel: scsi 4:0:0:31: Direct-Access     DELL     Universal Xport  0735 PQ: 0 ANSI: 5
Jun 13 17:41:09 hostname kernel: scsi 4:0:0:31: Attached scsi generic sg7 type 0
Jun 13 17:41:09 hostname kernel: scsi 4:0:0:31: Embedded Enclosure Device

Note that the same array is discovered fine on RHEL 5.7 box:

mptsas: ioc0: attaching ssp device: fw_channel 0, fw_id 5, phy 0, sas_addr 0x5001ec94f207a404
  Vendor: DELL      Model: MD3000            Rev: 0735
  Type:   Direct-Access                      ANSI SCSI revision: 05
sdc : very big device. try to use READ CAPACITY(16).
SCSI device sdc: 5761452032 512-byte hdwr sectors (2949863 MB)
sdc: Write Protect is off
sdc: Mode Sense: 77 00 10 08

where /dev/sdc block device is created. What is the problem here? Is some kernel module missing?. Is mptsas kernel module responsible for this?