Problem getting handle via CreateFile() when opening a SCSI tape drive via \\.\TAPE0, but only when tape is busy running microsoft backup

BTW, see also http://msdn.microsoft.com/en-us/library/aa362520(VS.85).aspx ("Creating a Backup Application"). According to this article, the parameters to 'CreateFile()' should be as follows:

HANDLE hTape;   // handle to tape device
 
hTape = CreateFile(TEXT("\\\\.\\TAPE0"),         // tape dev to open
                   GENERIC_READ | GENERIC_WRITE, // read/write access
                   0,                            // not used
                   0,                            // not used
                   OPEN_EXISTING,                // req for tape devs
                   0,                            // not used
                   NULL);                        // not used
                                              

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GetLastError returns 20h, ERROR_SHARING_VIOLATION

jkr:  I tried your suggestion, handle = CreateFile(DriverDev,GENERIC_READ|GENERIC_WRITE,0,0,OPEN_EXISTING,0,NULL);
got same error (when tape was streaming, of course.  Never a problem when the windows backup isn't running.  I can't imagine that MSFT created a situation where exclusive access is prevented for pass-through, this would break the O/S, and defeat the purpose of running something like GetTapeStatus to see if the tape is busy in the first place!

If another application has opened the tape drive, and has locked access to it, then I'd expect the OS to refuse your request to open it, particularly if you've set the GENERIC_WRITE flag. What happens if you just open it using GENERIC_READ?

If it still fails to open you may be able to access the drive by talking to the controller, and getting it to pass your SCSI requests through to the drive.

Not that I've ever tried it ;-)

PS, I don't think GetTapeStatus will return lock status... according to my documentation, the only statii it will return are:

ERROR_BEGINNING_OF_MEDIA
ERROR_BUS_RESET
ERROR_END_OF_MEDIA
ERROR_FILEMARK_DETECTED
ERROR_SETMARK_DETECTED
ERROR_NO_DATA_DETECTED
ERROR_PARTITION_FAILURE
ERROR_INVALID_BLOCK_LENGTH
ERROR_DEVICE_NOT_PARTITIONED
ERROR_MEDIA_CHANGED
ERROR_NO_MEDIA_IN_DRIVE
ERROR_NOT_SUPPORTED
ERROR_UNABLE_TO_LOCK_MEDIA
ERROR_UNABLE_TO_UNLOAD_MEDIA
ERROR_WRITE_PROTECT

Can you try ProcessExplorer (http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx) to see which other process (if any) is using the device in question?

Hi TapeDude, My original logic was CreateFile("\\\\.\\TAPE0",GENERIC_READ,FILE_SHARE_READ,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_READONLY,NULL);
I've pretty much tried every combination trying GENERIC_READ|GENERIC_WRITE, and FILE_SHARE_READ|WRITE, with and without the READONLY; tried permutations with CREATE_ALWAYS instead of OPEN_EXISTING, as sell as FILE_ATTRIBUTE_READONLY both in and out.

I am doing everything as administrator, and verified that I am logged into administrator.  I used sysinternals' process monitor and confirmed ntbackup is using \device\tape0, and looked at permissions, just to see if anything weird added.

GetTapeStatus won't work anyway because it is useless unless you can get a handle via the CreateFile.  

Even if I did know how to talk to controller directly it would be vendor/product specific, so can't go down that path.  Perhaps there is a mechanism to use an alias for \\.\TAPE0 ?   Is the O/S incapable of opening a tape drive that is using NTBACKUP for pass-through?    

>> and confirmed ntbackup is using \device\tape0

Well, so the error code is correct. Try to stop NTBackup and see if it works then.

This is why I used to use the ASPI layer! You could do whatever you liked to a drive, independent of the OS. But Adaptec stopped supporting ASPI after XP.

The only thing I can think of is to run a process at boot time that opens a handle to the drive and then just sits in memory, fielding your requests to/from the drive. But if NTBackup tries to lock the drive, it may fall over if Windows refuses to lock it; and if Windows DOES allow NTBackup to lock the drive, your process may not be able to access the drive.

You could try writing a dirty little command-line program that opens a handle to the drive, and then sits awaiting keyboard input. Meanwhile, run NTBackup and see what happens. If NTBackup runs, then try getting your command-line program to do a GetTapeStatus.

it works fine when ntbackup is not actively doing any thing to the tape.  I want to access the tape to perform pass-through regardless of whether or not ntbackup is running.  

So if you've already opened a handle to the drive, and then run NTBackup and get it to do something, calls to your existing handle fail?

>>I want to access the tape to perform pass-through regardless of whether or
>>not ntbackup is running.

Sorry, it's not a good idea to access a device that is in use by any means - be it a tape or anything else. That's what ERROR_SHARING_VIOLATION was created for.

"Sorry, it's not a good idea to access a device that is in use by any means"

True. Particularly to read or write! But assuming dlethe knows the dangers and is not actually setting tape modes or requesting/writing blocks, it shouldn't be a problem.

Be a good idea to ensure the "verify" setting is on in NTBackup though :-)

Respectfully, I've been writing storage diagnostics since the 90s, and know exactly what is safe.  What I am doing is safe.

I am sending SCSI inquires, LOG SENSE & MODE SENSE.  These are entirely safe.  The code works on a dozen other operating systems as well, just got the one stupid problem with windows locking me out on a tape while NTBACKUP is accessing it.    But I do want to say that I appreciate your comments.  If I was the expert in this particular case, I would have posted the same response as you :)

The technique works just fine, BTW, on \\.\PHYSICALDISK, SES/SAFTE enclosures, CDROMS/DVDs, and even certain RAID controllers. Just have the issue with windows tape drives & ntbackup.

>> What I am doing is safe.

I am not doubting that, not the least. But if NTBackup locks the device, there's no way to access it, sorry. And also sorry if I came across disrepectfully, I had no intention to do that.

So, now that we all we know we respect each other... ;-)

So if you've already opened a handle to the drive, and then run NTBackup and get it to do something, calls to your existing handle fail?

Sorry, don't have meeting of minds on if i open the tape handler first and keep it open, then run ntbackup ...

If I attempt this ,then NTBackup says "There is no free media available with the selected type. Ad unused media or click cancel to end the operation". Note: It may take up to 60 seconds to recognize new media".

So NTBACKUP also has a problem, but the message it returns is misleading.

The problem with that approach would be that NTBackup apparently requests exclusive access - now, if you have a handle open (even with shared access), NTBackup will fail.

It's not looking good... did you open the handle with GENERIC_READ, and FILE_SHARE_READ | FILE_SHARE_WRITE access?

The windows event log recorded RSM cannot manage library Tape0. Failed to communicate with device or obtain device setup information.   The Event ID is 168. Category None, Type: Error.  / Remote Storage Manager.

After googlin' RSM error 168, I found a promising link to "Qlogic Support Solution 12362". This is what the qlogic site said:
===============================

Tape backups are failing in Windows when the Removable Service Manager (RSM) is enabled. The server may be receiving Event ID: 168 errors.
Cause
      
This event occurs because Removable Storage Management (RSM) and some backup software applications are both trying to control the management of the robotic library.
Action
      
To correct this issue, disable the Removable Storage service, as described in the following paragraphs.
 
1. Enter Computer Management by right-clicking My Computer and selecting Manage.
2. Expand Services and Applications, then highlight Services.
3. Right-click on the Removable Storage Service and click Stop.
4. Double-click Removable Storage, and set the Startup type to Disabled. Click OK.
5. Exit Computer Management.
=====
My system had it as Manual.
Rebooting system now & will let you know after experimenting...

Well, it won't find a tape drive unless service is running.  Started service, started NTBACKUP on a big job, killed service, .. started my code.  Got same error as before ARRGGH!!