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--- title: Azure Elastic SAN configuration best practices description: Learn best practices for optimizing Azure Elastic SAN performance. Get recommendations for client-side settings, MPIO, iSCSI configurations, and deployment sizing author: roygara ms.service: azure-elastic-san-storage ms.topic: concept-article ms.date: 01/09/2026 ms.author: rogarana ms.custom: sfi-image-nochange # Customer intent: As a cloud infrastructure administrator, I want to implement best practices for configuring an Elastic SAN, so that I can achieve optimal performance and resource efficiency for my storage solutions in a cloud environment. --- # Optimize the performance of your Elastic SAN This article provides guidance on how to get optimal performance with an environment that uses an Azure Elastic SAN. ## Client-side optimizations ### General recommendations #### Windows and Linux virtual machines - For the best performance, deploy your virtual machines (VMs) and Elastic SAN in the same zone and the same region. - VM storage I/O to Elastic SAN volumes uses VM network bandwidth, so traditional disk throughput limits on a VM don't apply to Elastic SAN volumes. Choose a VM that can provide sufficient bandwidth for production/VM-to-VM I/O and iSCSI I/O to attached Elastic SAN volumes. Generally, you should use Gen 5 (D, E, or M series) VMs for the best performance. - Enable **Accelerated Networking** on the VM during creation. To learn how to enable it by using Azure PowerShell or Azure CLI, or to enable Accelerated Networking on existing VMs, see [Use Azure PowerShell to create a VM with Accelerated Networking](../../virtual-network/create-vm-accelerated-networking-powershell.md). :::image type="content" source="media/elastic-san-best-practices/enable-accelerated-networking.png" alt-text="Screenshot of VM creation flow, enable accelerated networking highlighted." lightbox="media/elastic-san-best-practices/enable-accelerated-networking.png"::: - To achieve maximum IOPS and throughput limits, use 32 sessions per target volume for each volume. Use Multipath I/O (MPIO) on the client to manage these multiple sessions to each volume for load balancing. Scripts are available for [Windows](elastic-san-connect-windows.md), [Linux](elastic-san-connect-linux.md), or on the Connect to volume page for your volumes in the Azure portal, which uses 32 sessions by default. Windows software iSCSI initiator has a limit of maximum 256 sessions. If you need to connect more than eight volumes to a Windows VM, reduce the number of sessions to each volume as needed. #### Azure VMware Solution - Deploy your Elastic SAN in the same region and availability zone as your Azure VMware Solution cluster - Configure Private Endpoints before mounting your Elastic SAN volume as an external datastore - If you plan for your environment to ever have 16 nodes in an Azure VMware Solution cluster, use one of the following configurations, depending on which hosts you have: - AV36, AV36P, AV52 - Six iSCSI sessions over three Private Endpoints - AV64 - Seven iSCSI sessions over seven Private Endpoints - If your environment won't have 16 nodes, use one of the following configurations: - AV36, AV36P, AV52 - Eight iSCSI sessions over four Private Endpoints - AV64 - Eight iSCSI sessions over eight Private Endpoints > [!NOTE] > When an Elastic SAN volume is attached to a cluster, it automatically attaches to all nodes. If you have 16 nodes and each node is configured to use eight iSCSI sessions, the configuration uses the maximum number of connections (128). Configuring your nodes to use seven iSCSI sessions ensures that if you need to attach an extra node (for maintenance) then you have available iSCSI sessions. - Use eager zeroed thick provisioning when creating virtual disks - Size ExpressRoute Gateway so that it can meet your throughput requirements - Configure your Elastic SAN to have at least 16 TiB in its base size, so you can get up to the maximum performance on your Elastic SAN datastores ### MPIO #### Windows Use the following commands to update your settings: ```powershell # Enable multipath support for iSCSI devices Enable-MSDSMAutomaticClaim -BusType iSCSI # Set the default load balancing policy based on your requirements. In this example, we set it to round robin which should be optimal for most workloads. mpclaim -L -M 2 # Set disk time out to 30 seconds Set-MPIOSetting -NewDiskTimeout 30 ``` For more information about MPIO cmdlets, see [MPIO reference](/powershell/module/mpio/). #### Linux Update the /etc/multipath.conf file by using the following commands: ```config defaults { user_friendly_names yes # To create ‘mpathn’ names for multipath devices path_grouping_policy multibus # To place all the paths in one priority group path_selector "round-robin 0" # To use round robin algorithm to determine path for next I/O operation failback immediate # For immediate failback to highest priority path group with active paths no_path_retry 3 # To disable I/O queueing after retrying once when all paths are down polling_interval 5 # Set path check polling interval to 5 seconds find_multipaths yes # To allow multipath to take control of only those devices that have multiple paths } devices { device { vendor "MSFT" product "Virtual HD" } } ``` #### Azure VMware Solution Microsoft manages MPIO settings for Azure VMware Solution. Optimal values are set when you create a datastore. ### iSCSI #### Windows Update the registry settings for iSCSI initiator on Windows. 1. Open Registry Editor: 1. Select **Start**, type `regedit` in the search box, and press **Enter**. 1. Navigate to the following location: [\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\\{4d36e97b-e325-11ce-bfc1-08002be10318}\0004 (Microsoft iSCSI Initiator)\Parameters] 1. Update the following settings. Right-click on each setting and select **Modify**. Change **Base** to **Decimal**, update the value, and select **OK**. |Description |Parameter and value | |---------|---------| |Sets maximum data the initiator sends in an iSCSI PDU to the target to 256 KB |MaxTransferLength=262144 | |Sets maximum SCSI payload that the initiator negotiates with the target to 256 KB |MaxBurstLength=262144 | |Sets maximum unsolicited data the initiator can send in an iSCSI PDU to a target to 256 KB |FirstBurstLength=262144 | |Sets maximum data the initiator can receive in an iSCSI PDU from the target to 256 KB |MaxRecvDataSegmentLength=262144 | |Disables R2T flow control |InitialR2T=0 | |Enables immediate data |ImmediateData=1 | |Sets timeout value for WMI requests to 30 seconds |WMIRequestTimeout = 30 seconds | |Sets timeout value for link down time to 30 seconds |LinkDownTime = 30 seconds | > [!NOTE] > After updating registry settings for optimal performance, you must restart the VM for the changes to take effect. If you don't restart the VM, you will continue to use the default settings. In cluster configurations, ensure iSCSI initiator names are unique across all nodes that are sharing volumes. In Windows, you can update them via the iSCSI Initiator app. 1. Select **Start**, search for **iSCSI Initiator** in the search box. This action opens the iSCSI Initiator. 1. Select **Configuration** to see the current initiator name. :::image type="content" source="media/elastic-san-best-practices/iscsi-initiator-config-widnows.png" alt-text="Screenshot of iSCSI Initiator configuration on Windows." lightbox="media/elastic-san-best-practices/iscsi-initiator-config-widnows.png"::: 1. To modify it, select **Change**, enter new initiator name, and select **OK**. :::image type="content" source="media/elastic-san-best-practices/update-iscsi-initiator-name-windows.png" alt-text="Screenshot of updating the iSCSI Initiator Name on Windows." lightbox="media/elastic-san-best-practices/update-iscsi-initiator-name-windows.png"::: #### Linux Update the following settings with recommended values in the global iSCSI configuration file (`iscsid.conf`, generally found in the `/etc/iscsi` directory) on the client before connecting any volumes to it. When you connect a volume, a node is created along with a configuration file specific to that node. For example, on Ubuntu VMs, you can find it in the `/etc/iscsi/nodes/$volume_iqn/portal_hostname,$port` directory. This configuration file inherits the settings from the global configuration file. If you already connected one or more volumes to the client before updating the global configuration file, update the node-specific configuration file for each volume directly or use the following command: ``` # Variable declaration volume_iqn=<Elastic SAN volume IQN> portal_hostname=<Elastic SAN volume portal hostname> port=3260 # Set maximum data the initiator sends in an iSCSI PDU to the target to 256 KB sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.conn[0].iscsi.MaxXmitDataSegmentLength -v 262144 # Set maximum SCSI payload that the initiator negotiates with the target to 256 KB sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.session.iscsi.MaxBurstLength -v 262144 # Set maximum unsolicited data the initiator can send in an iSCSI PDU to a target to 256 KB sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.session.iscsi.FirstBurstLength -v 262144 # Set maximum data the initiator can receive in an iSCSI PDU from the target to 256 KB sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.conn[0].iscsi.MaxRecvDataSegmentLength -v 262144 # Disable R2T flow control sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.session.iscsi.InitialR2T -v No # Enable immediate data sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.session.iscsi.ImmediateData -v Yes # Set timeout value for WMI requests sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.conn[0].timeo.login_timeout -v 30 sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.conn[0].timeo.logout_timeout -v 15 # Enable CRC digest checking for header and data sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.conn[0].iscsi.HeaderDigest -v CRC32C sudo iscsiadm -m node -T $volume_iqn -p $portal_hostname:$port -o update -n node.conn[0].iscsi.DataDigest -v CRC32C ``` > [!NOTE] > After updating iSCSI configuration files, restart the VM to ensure the new settings are applied. In cluster configurations, ensure iSCSI initiator names are unique across all nodes that are sharing volumes. In Linux, modify `/etc/iscsi/initiatorname.iscsi` to update the initiator name. :::image type="content" source="media/elastic-san-best-practices/update-iscsi-initiator-name-linux.png" alt-text="Screenshot updating the iSCSI Initiator Name on Linux." lightbox="media/elastic-san-best-practices/update-iscsi-initiator-name-linux.png"::: #### Azure VMware Solution Microsoft manages iSCSI settings. Optimal values are set when you create a datastore. ## Elastic SAN optimizations Before deploying an Elastic SAN, determine the optimal size for your deployment to achieve the right balance of performance for your workloads and cost. Use the following steps to determine the best sizing for you: With your existing storage solution, select a time interval (day, week, or quarter) to track performance. The best time interval is one that provides a good snapshot of your applications and workloads. Over that time period, record the combined maximum IOPS and throughput for all workloads. If you use an interval higher than a minute, or if any of your workloads have bottlenecks with your current configuration, consider adding more base capacity to your Elastic SAN deployment. Leave some extra capacity when determining your base capacity to account for growth. Use additional-capacity storage for the rest of your Elastic SAN to save on cost. For more information on performance, see [Elastic SAN and virtual machine performance](elastic-san-performance.md).