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SAT with UAS under Linux
Table of Contents
Overview
As mentioned on the 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 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 list of devices affected depends on the kernel version, and may include all Seagate enclosures, Initio INIC-3069 and 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 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 Kernel Parameters Documentation.
You can easily check to see whether the kernel using uas or usbstorage for a particular device using the lsusb -t command:
# lsusb -t
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 10000M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 480M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 5000M
|__ Port 1: Dev 11, If 0, Class=Mass Storage, Driver=usb-storage, 5000M
[...]
or
# lsusb -t
/: Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 10000M
/: Bus 03.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 480M
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 5000M
|__ Port 1: Dev 8, If 0, Class=Mass Storage, Driver=uas, 5000M
[...]
Alternatively you can check the messages that appear in kern.log when the device is first connected and look for the driver name mentioned at the end of the "scsi hostN" line:
usb 2-1: new SuperSpeed USB device number 8 using xhci_hcd usb 2-1: New USB device found, idVendor=NNNN, idProduct=NNN usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [...] scsi host4: uas scsi 4:0:0:0: Direct-Access VENDOR-NAME 0204 PQ: 0 ANSI: 6 sd 4:0:0:0: Attached scsi generic sg2 type 0 sd 4:0:0:0: [sdc] 1953525168 512-byte logical blocks: (1.00 TB/932 GiB) sd 4:0:0:0: [sdc] 4096-byte physical blocks sd 4:0:0:0: [sdc] Write Protect is off sd 4:0:0:0: [sdc] Mode Sense: 53 00 00 08 sd 4:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA sdc: sdc1 sdc2 sd 4:0:0:0: [sdc] Attached SCSI disk
or
usb 2-1: new SuperSpeed USB device number 9 using xhci_hcd usb 2-1: New USB device found, idVendor=NNNN, idProduct=NNNN usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3 [...] usb-storage 2-1:1.0: USB Mass Storage device detected scsi host4: usb-storage 2-1:1.0 scsi 4:0:0:0: Direct-Access VENDOR-NAME 0204 PQ: 0 ANSI: 6 sd 4:0:0:0: Attached scsi generic sg2 type 0 1953525168 512-byte logical blocks: (1.00 TB/932 GiB) sd 4:0:0:0: [sdc] Write Protect is off sd 4:0:0:0: [sdc] Mode Sense: 47 00 00 08 sd 4:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA sdc: sdc1 sdc2 sd 4:0:0:0: [sdc] Attached
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 drivers/usb/storage/uas-detect.h combined with the list of entries found in the 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
Workarounds
There are two approaches to getting smartmontools to work with one of these devices, both involving setting a "quirks" flag for the device in question.
- If you just want to get smartmontools working again and don't care about the performance improvements the come from using UAS mode, you can simply use the IGNORE_UAS flag to tell Linux to stick with the usb-storage mode instead, by using the "u" flag on the
usb-storage.quirkssetting.
- If you want to continue using UAS mode and are sure your particular device does properly support SAT mode even though the kernel detects it as a device that does not (e.g. as described in ticket:971#comment:12) , you can override that default configuration by passing an empty flag list in the
usb-storage.quirkssetting.
Note that in either case, you will need to find the idVendor and idProduct fields for your device, in 4-digit hex format. This information is found in the New USB device found, idVendor=NNNN, idProduct=NNNN
kern.log line, or in the output from "lsusb". (In the option strings below, the 4-digit numbers can optionally be preceded a "0x" prefix.)
Permanent Flag Settings
The usb-storage.quirks option is part of the more general mechanism for setting kernel/module options, and the exact mechanisms available for setting it will vary depending on your distribution. In brief:
- if your system has the "usb-storage" driver compiled as a loadable kernel module, you can set it by creating a file (e.g.
disable_uas.conf) under/etc/modprobe.d/containing the line (with the proper id numbers substituted)options usb-storage quirks=0bc2:231a:u
to disable UAS for that device (or
options usb-storage quirks=0bc2:231a:to try overriding the default NO_ATA_1X flag).
You will then probably need to follow your distribution's instructions for rebuilding your initramdisk in order to make the change apply when usb-storage drives are detected upon initial bootup.
- If the "usb-storage" driver is built in to the kernel, or if you simply prefer to make this change at the boot level rather than under /etc/modproble.d/, you can pass the option to the kernel as part of your boot configuration. For example, if your system uses grub2, you can edit
/boot/grub/defaultso that in includes a line similar toGRUB_CMDLINE_LINUX="usb_storage.quirks=0bc2:231a:u"
and then run
update-grub, and then reboot.
(Note that while the basic information used in these two approaches in the same, the punctuation used is different.)
In either case, you can then try plugging your USB device in again, and confirm using one of the methods above that the change had taken effect. (Note that if you use the :u flag, the kern.log messages generated when the device is detected should now include
usb 2-1: UAS is blacklisted for this device, using usb-storage instead usb-storage 2-1:1.0: USB Mass Storage device detected usb-storage 2-1:1.0: Quirks match for vid 0bc2 pid ab38: 800000 scsi host4: usb-storage 2-1:1.0
Temporary Settings
If you would like to temporarily set the quirks flag rather than making a permanent change (e.g. in order to run smartctl manually at some point but continuing to use UAS mode normally when using the drive for data transfers), you can do so by dynamically updating the module configuration.
First, unmount/unplug the USB device, then run the following commands (as root):
# cat /sys/module/usb_storage/parameters/quirks # echo "0x0bc2:0x231a:u" > /sys/module/usb_storage/parameters/quirks # cat /sys/module/usb_storage/parameters/quirks 0x0bc2:0x231a:u
(Note that the "echo" command completely replaces the current setting, so the first "cat" command makes sure that no quirks have been previously configured; it should just show a blank line.)
At this point you can plug the device's USB cable back in, and (after confirming via lsusb/kern.log that the device is connected to the usb-storage driver) you can then proceed to access the device using SAT.
A quirk set in this manner will automatically get cleared the next time the system is rebooted, but if you want to clear it more quickly you can simply execute:
# echo "" > /sys/module/usb_storage/parameters/quirks
to clear the configuration for the next time the device is plugged in.
Useful Links
A few pages with useful additional information:
General info:
- StackExchange: How can I check whether USB3.0 UASP (USB Attached SCSI Protocol) mode is enabled in Linux?
- Suze:USB 3.0 Hard Drive troubleshooting
Examples of the problems that originally triggered the current kernel behavior:
