VM Explorer Practitioner Forum

VM Explorer Backup to Tape - Transfer Rate Slow

New Member.

VM Explorer Backup to Tape - Transfer Rate Slow

Dear Community and/or Dear HP,


we currently use the Version 6.2 of your great VM Explorer and are testing the Options of Backup to Tape Drive.

We have a PCI-Express SCSI Card in the Backup Server connected via U320 SCSI to a Quantum Superloader 3 - LTO4 Tape Autoloader. 

From a functional perspective all is working as expected, but the Performance of the Tape Drive is not so good.

When using the same drive under Linux with Bacula/Baroes we get approx. 75 MB/s throughput with the same files (vhdx).

Under Windows using VM Explorer to write directly to the Tape we see about 50 MB/s.

In Linux we set the default LTO 4 Block Size from 64K to 256K for the speed Improvements, but in Windows I have not found any option sofar to increase this parameter.

Is it possible to configure VM Explorer to use 256K Blocksite as default for our LTO4 Drive ?

When I enable compression the throughput is even less.

Perhaps someone could give me a hint on if it is possible to change the LTO default Blocksize in Windows or VM Explorer or even knows where and how.


Many many thanks in advance for your help.



Ashok Goyat
Respected Contributor.

Re: VM Explorer Backup to Tape - Transfer Rate Slow


You may need to modify parameter value  of "MaximumSGList" in registry.  Identify adaptor installed on windows and look for registry value "MaximumSGList".

For example, the parameter for adaptor ql2300 will list under following registry -


Use the following formula to calculate the value of the MaximumSGList:

MaximumSGList = (BlockSize/4096) + 1

The procedure depends on the host bust adapter type: SCSI, Fibre Channel, or iSCSI. Before changing the block size for a particular host bus adapter card, see the vendor documentation or contact the vendor support.

As an example - Refer to following adaptec article for more details -


Note - Take a backup of registry before you make any changes. OS needs to reboot after making changes in registry.

hope this helps.



New Member.

Re: VM Explorer Backup to Tape - Transfer Rate Slow

Hello again,

due to capacity requirements we have upgraded the Hardware to a Quantum Superloader 3 with LTO-7 Drive and SAS Connection.

I have read that the Registry Settings for MaximumSGList are not applicable anymore for SAS, I Quote:

"The registry settings of NumberOfRequests and
MaximumSGList are not used by StorPort and will have no effect on the
LSI_SAS3.SYS driver."

I did test the Settings for:


But without any noticable Speed Improvments.

Using the new Drive we only get approx. 30MB/s of throughput when backing up to Tape using Trilead.

Also enabling or disableing Compression does not make a difference.

When I use a different Backup to Tape Software or the Test Diag Tools from Manfucturer I see more than 100MB/s (up to 170MB/s for real data and upto 280MB/s from the Diag Tools).

Is there anyway to improve the Throughput Speed of Trilead with using a SAS LTO7 Drive ?

Can Trilead use variable blocksize? 


Any kind of Tips or Help would be highly appreciated.

Many thanks & Best Regards