Changes between Version 1 and Version 2 of SAT-with-UAS-Linux

Timestamp:

Aug 5, 2019, 3:24:43 AM (5 years ago)

Author:

Nathan Stratton Treadway

Comment:

--

SAT-with-UAS-Linux

@@ -7 +7 @@
 
 = SAT with UAS under Linux =
+
+
+== Overview ==
+
+As mentioned on the [wiki:USB USB devices and smartmontools] page, in certain situations the Linux "uas" driver disables SAT transfers, which prevents `smartmontools` (and other tools, e.g. `hdparm`) from communicating properly with the attached SATA device.  See [query:?keywords=~uas+linux related tickets] for examples.
+
+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
+[https://github.com/torvalds/linux/commit/7fee72d5e8f1e7b8d8212e28291b1a0243ecf2f1 all Seagate enclosures],
+[https://github.com/torvalds/linux/commit/bda13e35d584dabf52c9f77e0fe62683ac4d9f86 Initio INIC-3069] and
+[https://github.com/torvalds/linux/commit/673029fe9c16c95600bdaca4760673527af32edf VIA VL711].
+
+== Technical Details ==
+
+The problem is that certain USB-SATA-bridge chipsets do not properly pass SAT commands on to the SATA device when running in UAS mode, and to work around this problem Linux automatically enables the NO_ATA_1X flag for those chipsets.  This turns off SAT passthrough... which in turn means that smartmontools is prevented from communicating with the device.
+
+For many of these chipsets, SAT passthrough works correctly is the old [https://en.wikipedia.org/wiki/USB_mass_storage_device_class BOT] (`usb-storage` driver) mode, and so smartmontools may suddenly stop working when the kernel is upgraded to a version which supports UAS, or from one which did did not apply the flag for that device to a newer kernel which does.
+
+For more information on the usb-storage flags, search for the 'usb-storage.quirks' entry in the [https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html Kernel Parameters Documentation].
+
+The detailed selection logic used by the kernel to decide which devices get this flag can be found in the `uas_use_uas_driver()` function in the [https://github.com/torvalds/linux/blob/master/drivers/usb/storage/uas-detect.h drivers/usb/storage/uas-detect.h]  combined with the list of entries found in the [https://github.com/torvalds/linux/blob/master/drivers/usb/storage/unusual_uas.h drivers/usb/storage/unusual_uas.h]
+file.  (As far as smartmontools/SAT passthrough is concerned, only the NO_ATA_1X flag is significant.)
+
+There doesn't seem to be a definitive way to confirm that the NO_ATA_1X flag is in fact in effect for a particular device, but if it is the symptom will be that commands which rely on SAT show invalid data, e.g.
+
+{{{
+# smartctl -d sat -a /dev/sdb
+smartctl 6.6 2016-05-31 r4324 [x86_64-linux-4.15.0-33-generic] (local build)
+Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org
+
+Read Device Identity failed: scsi error unsupported field in scsi command
+
+A mandatory SMART command failed: exiting. To continue, add one or more '-T permissive' options.
+
+
+# smartctl -d sat -T permissive -a /dev/sdb
+smartctl 6.6 2016-05-31 r4324 [x86_64-linux-4.15.0-33-generic] (local build)
+Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org
+
+Read Device Identity failed: scsi error unsupported field in scsi command
+
+=== START OF INFORMATION SECTION ===
+Device Model:     [No Information Found]
+Serial Number:    [No Information Found]
+Firmware Version: [No Information Found]
+Device is:        Not in smartctl database [for details use: -P showall]
+ATA Version is:   [No Information Found]
+Local Time is:    Mon Aug 27 20:44:01 2018 CEST
+SMART support is: Ambiguous - ATA IDENTIFY DEVICE words 82-83 don't show if SMART supported.
+SMART support is: Ambiguous - ATA IDENTIFY DEVICE words 85-87 don't show if SMART is enabled.
+A mandatory SMART command failed: exiting. To continue, add one or more '-T permissive
+}}}
+
+or
+
+{{{
+# hdparm -I /dev/sdc
+
+/dev/sdc:
+SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0a 00 00 00 00 24 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
+
+ATA device, with non-removable media
+Standards:
+        Likely used: 1
+Configuration:
+        Logical         max     current
+        cylinders       0       0
+        heads           0       0
+        sectors/track   0       0
+        --
+        Logical/Physical Sector size:           512 bytes
+        device size with M = 1024*1024:           0 MBytes
+        device size with M = 1000*1000:           0 MBytes 
+        cache/buffer size  = unknown
+Capabilities:
+        IORDY not likely
+        Cannot perform double-word IO
+        R/W multiple sector transfer: not supported
+        DMA: not supported
+        PIO: pio0
+}}}
+
+
+== Permanent Workarounds ==
+
+
+
+== Short-term Workarounds ==
+