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What to do when 'USB Attached SCSI (UAS)' appear when removing USB disk device

Posted on 2016-10-20
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Last Modified: 2016-10-22
We have an external Seagate 3tb drive Backup Plus.  When trying to remove the device it displays the following error:

usbd
Other USB sticks and drives can be remove with no problem but this device gives this error.

Question,
Why it says "SCSI" when the computer has no SCI drives?
How can we disconnect this deice successfully?
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Question by:rayluvs
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Assisted Solution

by:rindi
rindi earned 200 total points
ID: 41852637
There is probably some utility reading or writing to the disk. You should wait until that has finished, or stop the utility before trying again. For example windows search could be indexing it, or your Antivirus is scanning it, or your backup software could accessing it etc.

I haven't yet seen UAS, but I suppose it is the way the device is emulated and presented to the system.
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by:dlethe
dlethe earned 300 total points
ID: 41852663
It is because a USB-attached device USES the SCSI protocol for any attached device.  Even an internal IDE disk will report as a SCSI device to the O/S.

This is part of the ANSI spec and mechanism.  The USB data protocol uses SCSI family commands.  Remember SCSI is not just a physical attachment description, it also is a protocol.

SAS disks are also SCSI devices, as well as fibrechannel.  Also SATA disks attached to a SAS expander are considered SCSI.
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Author Comment

by:rayluvs
ID: 41852687
Understood on the SCSI (UAS).

What about yow can we disconnect this device successfully?

Makes sense that it may be apps we don't see such as windows search indexing the data or and Antivirus is scanning it, but if so, how can we go about it?

Beside waiting, which we did, it's pretty long time, what else can we do?

One thin we were recommended was to go into Disk Management and place the external drive as Offline, then disconnect device.  But we don't know if that will damage the device?

Please advice.
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Expert Comment

by:dlethe
ID: 41852708
you have some program that is running that has open files on the device.  You have to kill them first or you WILL end up with data corruption at some point.  Why the corruption??  Because the device is open in read/write mode, and write caching is certainly involved along with open files.

There are windows utilities that will tell you what programs have certain files opened.   Going to disk management isn't going to help. you have to make sure device is disabled for indexing, and disable write cache (which is profoundly risky to have enabled with a mountable USB disk anyway) ..

Plus anti-virus, and any other service just to start. bottom line something is going through files on that drive, you have to exclude it.
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Expert Comment

by:rindi
ID: 41852731
Right click the disk, select "Properties", and then uncheck "Allow files on the drive to have contents indexed ....", click on OK and wait until it has finished. That will disable indexing on the disk. You should also be able to exclude the external disk from your AV scans (if the disk is used for backups, it shouldn't have to be scanned as your original files should already have gone through the scan.
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Author Comment

by:rayluvs
ID: 41852780
Thanx, we disabled the device indexing also external drive has been in Quick Removal (disable write cache) since we purchased it.  Waited for while and tried to "eject" and same error.

We also disable AntiVirus, AntiSpyware and AntiMalre... Waited for while and tried to "eject" and same error.

Also removed from memory explorer and bringing it back, same error.
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Expert Comment

by:dlethe
ID: 41853043
Use MSFT's process explorer to see what apps are accessing the device
https://technet.microsoft.com/en-us/sysinternals/processexplorer.aspx
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Expert Comment

by:dlethe
ID: 41853050
You also just might look at full file listings on the external device and see if you can find any files that have been accessed in last X hours, or any new files added/modified.  That might give you a clue.  

SOMETHING, perhaps even some malware is accessing the device and leaving open handle(s).   Otherwise you would be able to eject.   Process explorer will find out what is going on, but you will have to dig.
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Author Comment

by:rayluvs
ID: 41853217
Ok, a summary:

We noticed that when this happens to the drive is when we open a TrueCrypt volume.  Yet we closed the TC drive and delete the TC apps from memory, but same thing; error.  Without TC, it will remove the USB device successfully but if we run TC and open then after use close or dismount the volume, same problem: can't remove device.

In conclusion, these are all that things we have done that didn't work:

  • Make sure nothing is accessing the USB drive like AV, Multimedia players, etc
  • Use Process Explorer software  (close handle of the drive)
  • Remove from command prompt (RunDll32.exe shell32.dll,Control_RunDLL hotplug.dll)
  • Disable System Protection of the USB drive
  • Turn off Indexing for drive
  • Log off and logon
  • Disk Management option >> Drive Offline

The only thing that worked was:
  • Restart

Any additional advice?
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Expert Comment

by:dlethe
ID: 41853249
Well then you know TrueCrypt has this bug (or feature depending on a point of view).  So you're just going to have to contact them and report this problem and see if there is a workaround.
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Author Comment

by:rayluvs
ID: 41853581
Nope, it's not TrueCrypt.  We also have TC volumes in other USB external drives and we can remove them after working with the volumes.  So it must be the Seagate 3tb drive Backup Plus.

There has to be something specific to this drive that it causes it NOT to be removed (FYI, see ID: 41853217 for all our test to-date).
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Expert Comment

by:dlethe
ID: 41853597
It IS TrueCrypt.  That is the software package that is in play.  I assure you, there is no code within TrueCrypt along the lines of:

if (HDDModel == Seagate3TBBackupPlus)
  goto hang;
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Author Comment

by:rayluvs
ID: 41853632
Well, we think yes or no; strange whats going on.

We took out 7 usb external drives we have where 4 of them have TC volumes.  After connecting them, opening their TC volumes, closing, them, it worked!  Even the same ' Seagate 3tb drive Backup Plus' worked!

We did various times.

Is there way of using the Process Explorer to try to identify the problem, besides the 'close handle of the drive' ?  (or some tool that would monitor the behavior so we can see where it is happening)


Update:
Our Western Digital drive we just opened TC and closed, problem occur.

We check Process Monitor but can't seem to identify anything that will help us see what is happening.
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Expert Comment

by:dlethe
ID: 41853786
Process explorer is designed to solve this sort of problem.  You can see what files/devices are opened by each application.   But you have to catch it in the act of opening and using the device handle.

Personally, i would contact the software vendor, and save some time.  Surely you aren't the only person having this issue.
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Author Comment

by:rayluvs
ID: 41854740
TrueCrypt is gone.  We have search for problems with Removable USB contain TC volumes and found nothing.

The best bet is  Process Monitor.  There has to be way of identifying it.
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Accepted Solution

by:
dlethe earned 300 total points
ID: 41855494
Read the syslog and see what, if any applications log something in event monitor when you try to eject.  That gives you the program that has handle opened to the drive.    Unfortunately, you have to tell process explorer what process to look at ahead of time.  

The other solution(s) require writing some code like a filter driver which is a big deal to code.   You could also install some USB monitoring software that detects and decodes all I/O going down the USB port, but you'd have to know what to look for  because it won't tell you what programs are running, it will give you raw decoded CDBs (like READ(10) which is the 10-byte read to get N blocks starting at physical offset #M.).  One could then figure out the contents of that data, and the contents of other I/Os and it would typically reveal what is going on so you could infer what application is doing it.  

 Bottom line, best bet is process monitor.  You *could* actually plug in the device, don't do any I/O on (intentionally),  then let it go through this process of complaining and yank it anyway, hopefully it would log something from an application.    Certainly there is risk of data corruption, but unless it is defragging or something similar it is likely file is opened read only so unlikely to cause any problem
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Author Comment

by:rayluvs
ID: 41855500
Thanx you very much!! Super great info!!!  Sat down with our assistant so to start this process!!!  We think with last entry is more than sufficient to identify the problem!!

Thanx, will close the question!
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