Version 15 (modified by Christian Franke, 5 years ago) (diff)

Explain failing SAT when UAS is enabled under Linux

USB devices and smartmontools

To access USB storage devices, the operating system sends SCSI commands through the USB transport to the device. If the USB device is actually a PATA or SATA disk in an USB enclosure, the firmware of its USB bridge chip translates these commands into the corresponding ATA commands. This works straightforward for read and write commands, but not for SMART commands.

To access SMART functionality, smartmontools must be able to send ATA commands directly to the disk. For USB devices, at least the following conditions must be met:

  • The USB bridge provides an ATA pass-through command.
  • This command is supported by smartmontools.
  • The operating system provides a SCSI pass-through I/O-control which works through its USB-layer.
  • SCSI support is implemented in the operating system interface of smartmontools.

Some recent USB bridges already support the vendor independent SAT (SCSI/ATA Translation, ANSI INCITS 431-2007) standard. Other USB bridges provide vendor specific ATA pass-through commands. The current version of smartmontools supports the following pass-through commands and USB bridges:

Command USB bridges smartctl option 48-bit ATA support Comment
SAT ATA pass-through 12 and 16 various (ASMedia, Initio, Oxford, newer JMicron, ...) -d sat[,16]; -d sat,12 requires '-d sat[,16]' Older Linux kernels may require '-d sat,12'
Cypress ATACB Cypress CY7C68300B/C (AT2LP), CY7C68310 (ISD-300LP) -d usbcypress[,CMD] No CY7C68300A (AT2) may not work.
JMicron ATA pass-through JMicron JM20329, JM20335-39, Prolific PL2507/3507 -d usbjmicron[,p][,x][,PORT] Yes (SATA only) '-d usbjmicron,x' enables 48-bit support
Prolific ATA pass-through Prolific PL2571/2771/2773/2775 -d usbprolific Yes SMART access via eSATA may not work (ticket #719)
Sunplus ATA pass-through Sunplus SPIF215/6, SPIF225/6 -d usbsunplus Yes

Smartmontools was successfully tested with many USB devices on several Platforms. If the USB ID can be obtained from the operating system, smartmontools also supports auto-detection of (the already tested) USB devices. Then it is not necessary to specify the '-d' option. See the following table for details:

Platform ...has SCSI pass-through smartmontools supports SCSI ... supports USB ... auto-detection ... in smartd DEVICESCAN Comment
Linux Yes Yes YES YES YES May not work with UAS, see below
Mac OS X No No (Yes) (Yes) (Yes) via OS-X-SAT-SMART-Driver, see below
NetBSD Yes Yes YES No No
OpenBSD Yes Yes YES No No
Solaris Yes Yes YES No No
QNX ? No No No No
OS/2 No No No No No
Windows Yes Yes YES YES YES

If UAS transfer mode is enabled under Linux, -d sat[,12] may fail with error message scsi error: unsupported field in scsi command (see ticket #971). This is because the Linux kernel rejects SAT ATA pass-through commands for certain devices with broken pass-through support. This depends on Kernel version and may include all Seagate enclosures, Initio INIC-3069 and VIA VL711.

The OS X SAT SMART Driver provides access to SMART data for SAT, JMicron and Sunplus capable USB and Firewire devices on Mac OS X. On OSX El Capitan (10.11+) you may need a signed driver, which can be downloaded from the DriveDx website. Note that this does not support 48-bit ATA commands (-l xerror) or non-SMART ATA commands (-s apm,N). Full USB support would require SCSI pass-through support which does not yet exist on Mac OS X.