Best practices for using vSAN iSCSI targets

Products

• VMware vSAN

Issue/Introduction

This article provides information on best practices when hosting iSCSI targets from vSAN clusters.

Environment

VMware vSAN (All Versions)

Resolution

The iSCSI LUNs hosted on vSAN are essentially large empty virtual disk (VMDK) container objects that are managed and protected by storage policy configurations. This means that the properties of these objects can be modified without bringing the LUNs offline. For instructions on configuring iSCSI as a service, see the Using the vSAN iSCSI Target Service section in the Administering VMware Virtual SAN guide  (Use the Product version drop down for vSAN versions in the link)

Key benefits

• Supports Windows Server Failover Cluster (WSFC)
• Performance service improvements for iSCSI targets
• Preferred method for mapping VMDKs to physical Oracle RAC deployments
• Improvements for sharing vSAN resources with physical workloads
• Support for CHAP & Mutual CHAP authentication methods
• iSCSI target objects are protected according to storage policies
• Simplified storage management through the use of vCenter, vSAN API and PowerCLI

Current Limitations

• Unsupported usage as a target for other ESXi hosts
• Unsupported usage with third-party hypervisors
• Migrations using raw device mapping (RDMs)
• No support for Multiple Connections per Session (MCS)

Configuration maximums

• Maximum 1024 LUNs per vSAN cluster
• Maximum 128 targets per vSAN cluster
• Maximum 256 LUNS per target
• Maximum LUN size of 62TB
• Maximum 128 iSCSI sessions per host
• Maximum 4096 iSCSI IO queue depth per host
• Maximum 128 outstanding writes per LUN
• Maximum 256 outstanding IOs per LUN
• Maximum 64 client initiators per LUN

Supported Operating Systems

For WSFC support, see Using SQL Server Failover Clustering on a vSphere 6.7 vSAN Datastore with vSAN iSCSI Target Service: Guidelines for supported configurations. 

New updates in 7.0 U1 vSAN from iSCSI perspective to existing:

• vSAN stretched cluster is supported with iSCSI configuration. 
• The handling of cross site iSCSI traffic between the initiator and target has been enhanced compare to previous version. Supports IO owner location config in stretched cluster to avoid cross site iSCSI traffic.  

 

Additional Information

To see the configuration maximums for vSAN iSCSI per vSAN version use the configmax tool.

For versions 6.x - 8.x:

1. Filters > VMware > vSphere
   
   
   
   
2. Select the version, check vSAN and then click on "View Limits"
   
   

For version 9.x  

1. Select vSAN under "VMware Cloud Foundation"
   
   
   
   
2. Select the version, check vSAN and then click on "View Limits"