(DP) Support Tip: How the data device SCSI address is created

[Tadashi]

Topic
How is the data device SCSI address for Tape Devices created on Windows system ?

Ex.) Tape1:0:1:0C

Response
The data device SCSI address is formed by Scsi Bus number , Target Id , Logical Unit Id and Drive Index .

Those values can be seen in Windows registry HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\Scsi .


Ex.)
HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\Scsi\Scsi Port 3\Scsi Bus 0\Target Id 0\Logical Unit Id 0
DeviceName : Changer0

The data device SCSI address for this device will be formed as Changer0:0:0:0 .

HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\Scsi\Scsi Port 3\Scsi Bus 0\Target Id 1\Logical Unit Id 0
DeviceName : Tape1

The data device SCSI address for this device will be formed as Tape1:0:1:0C .

"Tape1" means Drive Index is "1" .

[MFranca86]

Thanks for the tip.
Can you tell me why the addresses are changed every time the MA is restarted?

Sometimes they are re-created with the same address as other MA occurring duplicate paths.

[Sebastian.Koehler]

Hi @MFranca86,

The change of the data device on the Media Agent happens in SAN environments due to the nature how Windows discovers and enumerates devices along the SCSI bus. If you have HP/HPE tape drivers installed, you might use the following addition to Windows registry to have persistent devices across server reboots.

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Tape]
"Persistence"=dword:00000001

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\MChgr]
"Persistence"=dword:00000001

This works well and is fully supported.

Regards,
Sebastian Koehler

[MFranca86]

Thanks, I already made the changes in MA.

[MFranca86]

Didn't work.

After restart my MA, all my SCSI Address has been changed.

[KenKrubsack]

MFranca86,

Are you in a SAN environment (meaning, is the tape unit SAN attached) or is this a locally attached device?

Ken

[Sebastian.Koehler]

Hi @MFranca86,

After restart the device they will change once (to the long persistent format) but will never change again.

Regards,
Sebastian Koehler

[MFranca86]

OK,
So that's it, I saw that the new addresses are now quite long.

@KenKrubsack  it's a SAN Environment.

[Sebastian.Koehler]

Hi @MFranca86,

So you're all set now and device persistence is in place. You will notice the difference after the next reboot.

Regards,
Sebastian Koehler

[KenKrubsack]

MFranca86,

Yeah, once you go persistent, the addresses go to what is called a two's-complement (basically a negative number).

The other thing I always did was to go into my media servers (the ones that actually talked to the tape drives) and locked down which LUNs went to which drives.  I did it with Emulex HBAs - never messed with QLogic HBAs.

Once you have these locked down on ALL of your media servers, this should help.

I also added this registry hack on the media servers:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\hplto]
"AutoRun"=dword:00000000

which kept some of the startup scans from running and possibly changing those IDs.

Ken