Monday, August 06, 2012


 Got an eSATA / USB3.0 Dual Bay HDD Dock:
  1. http://www.vantecusa.com/en/product/view_detail/494
  2. http://www.amazon.com/gp/product/B007XJIYRC/
The first impression is incredibly both bay cannot work at same time, then I found it's actually because of CONFIG_SCSI_MULTI_LUN not default enabled: under USB mode, the dock is assuming having 2 luns, SCSI-3 standard has REPORT_LUN command but seems this device doesn't responds REPORT_LUN query, so it assumes only 1 lun, found 1 drive only; we can do a manual scan:

echo '- - 1' >/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.1/2-1.1:1.0/host12/scsi_host/host12/scan

After that the kernel scsi_mod middle layer would scan lun 1, found the 2nd drive; or could learn from Linux USB Frequently Asked Questions: or add scsi_mod.max_luns=2 to kernel boot parameter

(http://www.linux-usb.org/), "options scsi_mod max_luns=2" (updated to latest linux kernel v3.5)
$ dmesg
[15011.760697] usb-storage 2-1.1:1.0: usb_probe_interface
[15011.760709] usb-storage 2-1.1:1.0: usb_probe_interface - got id
[15011.760806] scsi12 : usb-storage 2-1.1:1.0
[15012.762244] scsi 12:0:0:0: Direct-Access     ST910006 40NS             CC01 PQ: 0 ANSI: 5
[15012.762847] sd 12:0:0:0: Attached scsi generic sg2 type 0
[15012.763368] sd 12:0:0:0: [sdb] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB)
[15012.763787] scsi 12:0:0:1: Direct-Access     WDC WD16 00AAJS-00YZCA0   01.0 PQ: 0 ANSI: 5
[15012.764013] sd 12:0:0:1: Attached scsi generic sg3 type 0
[15012.764584] sd 12:0:0:0: [sdb] Write Protect is off
[15012.764587] sd 12:0:0:0: [sdb] Mode Sense: 23 00 00 00
[15012.765111] sd 12:0:0:1: [sdc] 312581808 512-byte logical blocks: (160 GB/149 GiB)
[15012.765865] sd 12:0:0:0: [sdb] No Caching mode page present
[15012.765871] sd 12:0:0:0: [sdb] Assuming drive cache: write through
[15012.766619] sd 12:0:0:1: [sdc] Write Protect is off
[15012.766625] sd 12:0:0:1: [sdc] Mode Sense: 23 00 00 00
[15012.767612] sd 12:0:0:1: [sdc] No Caching mode page present
[15012.767618] sd 12:0:0:1: [sdc] Assuming drive cache: write through
[15012.769723] sd 12:0:0:0: [sdb] No Caching mode page present
[15012.769726] sd 12:0:0:0: [sdb] Assuming drive cache: write through
[15017.751786] sd 12:0:0:1: [sdc] No Caching mode page present
[15017.751795] sd 12:0:0:1: [sdc] Assuming drive cache: write through
[15022.187904]  sdc: sdc1 sdc2 < sdc5 >
[15022.216575] sd 12:0:0:1: [sdc] No Caching mode page present
[15022.216580] sd 12:0:0:1: [sdc] Assuming drive cache: write through
[15022.216584] sd 12:0:0:1: [sdc] Attached SCSI disk
[15022.222847]  sdb: sdb1 sdb2 sdb4 sdb5
[15022.227795] sd 12:0:0:0: [sdb] No Caching mode page present
[15022.227800] sd 12:0:0:0: [sdb] Assuming drive cache: write through
[15022.227802] sd 12:0:0:0: [sdb] Attached SCSI disk
Well recognized: 
$ lsscsi -gv
[12:0:0:0]   disk    ST910006 40NS             CC01  /dev/sdb   /dev/sg2
[/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.1/2-1.1:1.0/host12/target12:0:0/12:0:0:0]
[12:0:0:1]   disk    WDC WD16 00AAJS-00YZCA0   01.0  /dev/sdc   /dev/sg3 
[/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.1/2-1.1:1.0/host12/target12:0:0/12:0:0:1]
When attached to USB 2.0 ports, it archives 30MB/s sequential read/write performance, not as optimal as eSATA 100MB/s; This USB is actually "Mass Storage" / "SCSI" / "Bulk-Only" should be able to use uas (USB Attached SCSI) protocol, but not sure why uas drive not attached, a forced bind neither work

$ lsusb -d 174c:55aa -v
Bus 002 Device 003: ID 174c:55aa ASMedia Technology Inc. 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.10
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0        64
  idVendor           0x174c ASMedia Technology Inc.
  idProduct          0x55aa 

[...]
  Configuration Descriptor:
    Interface Descriptor:

      bInterfaceClass         8 Mass Storage
      bInterfaceSubClass      6 SCSI
      bInterfaceProtocol     80 Bulk-Only
# echo 2-1.1:1.0 > /sys/bus/usb/drivers/usb-storage/unbind
# echo 2-1.1:1.0 > /sys/bus/usb/drivers/uas/bind
write error: No such device
need another time to figure out why.

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