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iSCSI Gateway performance tuning for Veeam environments.

This document (7023150) is provided subject to the disclaimer at the end of this document.


SUSE Enterprise Storage 5
Veeam Backup & Replication 9.x


Tuning considerations for improving performance when the Veeam backup repository is hosted on Windows, the disks are backed by SUSE Enterprise Storage RBD (Rados Block Device) images and VMware Virtual Machine disk files are being backed up / restored.


A. Pool Type

Consider using Replicated Pools only for the RBD (Rados Block Device) images since the overhead involved with Erasure Coded Pools and the sequential type of backup / restore workload can result in a fairly large performance difference.

B. RBD image object-size

The default object-size for RBD images is 4MB. The default Windows iSCSI configuration limits the iSCSI I/O to 256k, it can be increased to for example 512k (see section C. below). Due to this, images to be used for the Veeam backup repository should be created with an object size of 1MB instead. Note that reducing the object size too much will result in a much higher number of RADOS objects per RBD which is also undesirable.

The object size of an image can be changed during creation, via openATTIC by adjusting the "Object size" parameter or if the image is created via the command line using:

rbd create $pool_name/$image_name --size xxxxM/G/T --object-size 1M

C. Increase the Windows iSCSI I/O size

It is needed to edit the registry of the Windows server and after the change it is required to reboot the server. 
To change this setting, edit the following key:

"[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e97b-e325-11ce-bfc1-08002be10318}\<MS iSCSI Initiator Instance Number>\Parameters]"

Note that the "...\<MS iSCSI Initiator Instance Number>\..." part of the above registry link will be something like "...\0001\..." or "...\0003\..." etc. To verify the correct key is being changed, expand the "PersistentTargets" key below the "Parameters" entry and verify the targets listed are the correct targets as exported via iSCSI.

Change the "MaxTransferLength" dword value to "0x00080000" (512K), it can also be tested with a value of "0x00100000" (1M).

D. Windows Multipath I/O (MPIO)

Using multiple iSCSI Gateways to export the target will allow using MPIO on the Windows client. Information on how to configure MPIO on Windows can be found in the online Microsoft Documentation, for example as described here.

To verify MPIO is configured properly running the below example command (and then making sure the target disk(s) are listed with multiple paths in the resulting "mpio.conf" file) can be used:

mpclaim.exe -v mpio.conf

E. Veeam Specific Settings

1. "Enable parallel processing" should be enabled.
2. "Enable storage latency control" should be disabled.

For information on the above two settings see the Veeam online documentation.

3. "Use per-VM backup files" should be enabled.

For more information on the above setting see the Veeam user guide for VMware.

4. The amount of parallel tasks should be adjusted appropriately for the environment to allow an optimal number of Virtual Machines to be backed up in parallel.

For more information on the above see the Veeam User Guide for VMware vSphere.


Additional Information

Also see TID 7023053 - iSCSI Gateway performance tuning for VMware environments


This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:7023150
  • Creation Date: 03-Jul-2018
  • Modified Date:03-Mar-2020
    • SUSE Enterprise Storage

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