I recently implemented a VMware farm utilizing Isilon as a backend datastore. Although Isilon’s specialty is sequential access I/O workloads such as file services, it can also be used as a storage for random access I/O workloads such as datastore for VMware farms. I only recommend it though for low to mid-tier VMware farms.

Isilon scale-out storage supports both iSCSI and NFS implementations. However, NFS implementation is far superior than iSCSI. The advantages of NFS are:

1. simplicity – managing virtual machines at the file level is simpler than managing LUNs,
2. rapid storage provisioning – instead of managing LUNs, all VMDK files may be stored on a single file export, eliminating the need to balance workloads across multiple LUNs,
3. higher storage utilization rates – VMDK files are thin-provisioned by default when using NAS-based datastore.

In addition, Isilon only supports software iSCSI initiators.

Isilon supports VAAI (vStorage APIs for Array Integration) which offloads I/O intensive tasks from the ESXi host to the Isilon storage cluster directly (such as when doing storage vmotion, virtual disk cloning, NAS-based VM snaphots, and VM instant provisioning), which results in overall faster completion times. Isilon also supports VASA (vStorage APIs for Storage Awareness) which presents the underlying storage capabilities to vCenter.

When using NFS datastore, it is very important to follow the implementation best practices which can be found here. Some of the important best practices are:

1. Connect the Isilon and ESXi hosts to the same physical switches on the same subnet. The underlying network infrastructure should also be redundant, such as redundant switches.
2. Use 10GB connectivity to achieve optimal performance.
3. Segment NFS traffic so that other traffic such as virtual machines network traffic or management network traffic do not share bandwidth with NFS traffic.
4. Use separate vSwiches for NFS traffic on the VMware and use dedicated NICs for NFS storage.
5. Use Smartconnect zone to load balance between multiple Isilon nodes, as well as dynamic failover and failback of client connections across the Isilon storage nodes.
6. Enable the VASA features and functions to simplify and automate storage resource management
7. To achieve higher aggregate I/O, create multiple datastores, with each datastore mounted via a separate FQDN/ Smartconnect pool and network interface on the Isilon cluster.