Case study about changing data block size settings for recording to tape with Veeam Backup & Replication

Original author: Kira Podlesnaja
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We continue a series of posts with analysis of real cases received by Veeam technical support. Today we will discuss the situation when the data block size settings made for the tape device in the Veeam console do not match the settings of the real device. Of course, we will give recommendations for tracking and correcting such an error.

I note that block resizing can also be done in cases where you need to increase data processing performance. Indeed, the larger the block size, the more data the device can record per unit of time.



Imagine this: the HBA is out of order and needs to be replaced. In this case, the Veeam server remains unchanged (that is, without reinstalling the OS and the Veeam application itself), as well as the device for recording to magnetic tape. You finally set everything up successfully, and then your boss needed to immediately restore the virtual machine from the backup recorded on tape the day before replacing the HBA. This is where the error message pops up with the block size: Error: Invalid block size

We are investigating


First, go to the Veeam backup server in the folder C: \ ProgramData \ Veeam \ Backup , where the logs are stored by default. In the log, our attempt to perform VM recovery will be reflected something like this:



We see that after replacing the controller our tape library did not allow us to set the previous block size for writing to tape:
[timestamp] <08> Info [AP] (0f3e) output: Cannot set block size: 1048576setMediaParameters error: Tape error: '87' (The parameter is incorrect.)

After we make sure that the log contains such entries, check what block size is specified in the tape device settings in the Veeam console . If it turns out to change it to the one that was specified when archiving to tape, then you solved the problem.

However, if the maximum block size is smaller than you expected, you will have to open Device Manager and see what block size is stamped there. If the maximum value exceeds the value specified in the Veeam Backup & Replication settings, then again we have a discrepancy in the settings, and the investigation will have to be continued.

Example


Here is an example from the real life of the user: in the Veeam console, the maximum block size is indicated as 512 KB.



However, earlier it was possible to choose a larger value. And in Device Manager, the maximum block size is actually 8 MB:



A reasonable question arises: why is there such a limited size in Veeam settings if the driver does not prohibit working with a much larger block size? And what can be done about it? Let's try to dig a little deeper to answer this question.

As we recall, only the HBA controller has changed. The documentation ( Best Practices for Veeam Backup & Replication ) about connecting via HBA says the following:

If you connect the tape devices via HBA, Veeam Backup & Replication uses the block size configured for the HBA.

If the tape device is connected via HBA, then Veeam Backup & Replication will use the block size specified in the HBA settings.


So, you need to find out what block size is now set in the HBA settings, and set the appropriate value for it.

Editing settings


For an example of editing HBA settings, consider HPE QLogic. HPE has a very official article on how to change the block size for QLogic HBA .

To configure QLogic, we need a special tool for working with the operating system of our tape device - we download it from here .

To see what block size is set, run the -tsize command , we see that in this example we have 512 KB.

Then we execute the same command with the key to set the new block size:
-tsize / fc / set 1024 or even -tsize / fc / set 2048 in general .



After we changed the settings for HBA, we need to return to Device Management (Device Manager ) and run a scan for hardware changes.

When the changes take effect, be sure to restart the Veeam Tape Service .

We expect that in the Veeam console it will now also be possible to set the maximum block size larger than it was until now. And our task, as we recall, is to set the block size equal to that which was when writing the backup to tape.

Indeed, in the console we now see two times the maximum block size:



A problem with a discrepancy in block sizes can occur not only during the recovery operation, but also during inventory and updating of the tape catalog. Therefore, we always recommend that you carefully read the restrictions and features of the settings, and if a discrepancy is found, then try to eliminate it. If you can’t do it yourself, we are always ready to help.

Your Veeam Support Team.

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