Comparing VMware VSA & VMware Virtual SAN

Today VMware announced the general availability of VMware Virtual SAN, a new, radically simple storagesolution optimized for virtual environments. With VMware Virtual SAN, VMware delivers its first Software-Defined Storage product.

What is vSAN

Virtual SAN is a distributed layer of software that runs natively as a part of the ESXi hypervisor. Virtual SAN aggregates local or direct-attached storage disks of a host cluster and creates a single storage pool shared across all hosts of the cluster.While supporting VMware features that require shared storage, such as HA, vMotion, and DRS, Virtual SAN eliminates the need for an external shared storage and simplifies storage configuration

VMware vSAN

Redefines the hypervisor to cluster both compute and storage
Pools locally attached SSDs and HDDs to create shared distributed storage
Based on scale-out architecture with built-in SSD read/write caching
Leverages VM-centric storage policy-based management for automation and self-tuning
Managed directly from vCenter Server

VMware vSAN initial use cases
Virtual Desktops
•    Handle peak performance such as boot, login, read/write storms
•    Seamless granular scaling from POC to deployment without huge upfront investments
•    Support high VDI density

Tier 2/3 applications and Test & Dev workloads
•    Rapid storage provisioning and complete automation
•    Ideal price/performance
•    Minimizes data center footprint

DR Target
•    Integrated with vSphere Replication and VMware SRM
•    Reduces cost of storage
•    Minimizes data center footprint

Customer Benefits
WMware recognizes the significant cost of storage in many virtualization projects. Many projects stall, or are canceled due to the fact that to meet the storage requirements of the project, the storage simply becomes too expensive.
Using a hybrid approach of SSD for performance and HDD for capacity, vSAN is aimed at re-enabling projects that require a less expensive storage solution.
•    Ridiculously easy to setup, configure & manage using the vSphere Web Client
•    Eliminate performance bottlenecks and single points of failure
•    Flexible – you can dynamically expand by either adding more disks to existing hosts or adding additional hosts
•    Lower storage TCO

vSAN is Resilient Against Disk, Host and  Network Failures. It also leverages distributed storage and cache mirroring to ensure data is never lost.


In case of a host failure:

1. VSAN data continues to be available without disruption

2. vSphere HA automatically restarts VMs on another host

3. VM SLA restored automatically

Key vSAN requirements


vCenter Server 5.5

Both Windows version of vCenter and the vCenter Server Appliance (VCSA) can support vSAN

vSphere 5.5

All vSphere host in the VSAN enabled cluster must have a VMkernel adapter configured for vSAN traffic.
A private 1Gb network is required, but 10Gb with Jumbo frames enabled end to end is highly recommended
Both Standard and Distributed virtual switches are supported. If using Standard virtual switches ensure that port group names for the VMKernal port are consistent on all hosts in the vSAN enabled cluster
A minimum of 3 and maximum of 32 vSphere hosts can be configured to contribute local storage to the vSAN enabled cluster. (Not all vSphere host in the cluster need to contribute storage)


vSphere hosts contributing storage to the VSAN cluster require the following:

A storage controller that supports either pass through or RAID 0 mode. At least one SAS or SATA Solid State Drive (SSD). This is used as the read/write cache for the vSAN Disk group. At least one SAS or SATA Hard Disk (HDD) and one host, SSDs and HDDs are combined into disk groups with a single SSD and up to six HDDs per a disk group. (The capacity ratio of an SSD to HDDs typically depends on use cases and workloads, but the best practice is to use 1:10 ratio of SSD capacity to HDD in each disk group.As a best practice all vSphere hosts contributing storage to the vSAN cluster should have identical configurations (Same number of disks and identical disk Group configuration

Characteristics of Virtual SAN

VSAN Interoperability

VSAN is fully integrated with the following VMware’s storage and availability features

•       VM snapshots
•       vSphere HA
•       DRS
•       vMotion
•       Storage vMotion
•       SRM/VR
•       VDP/VDPA
Limitations of Virtual SAN
•       Virtual SAN does not support multiple Virtual SAN clusters for each host.
•       Virtual SAN does not support virtual machines with large capacity virtual disks, or disks greater than 2TB.
•       Virtual SAN supports only SATA and SAS local storage. You cannot use storage attached through USB, Fibre Channel, or iSCSI.
•       Virtual SAN does not support such features as Fault Tolerance, vSphere DPM, and Storage I/O   Control.
•       Virtual SAN does not support native snapshots and SE Sparse disks.
•       Virtual SAN does not support SCSI reservations.

Characteristics of a Virtual SAN Cluster

  • Virtual SAN clusters can include hosts with storage disks, or without. The minimum requirement is three hosts with storage disks.
  • If a host contributes storage devices, it must have at least one SSD and one HDD device.
  • Virtual SAN takes up entire disks, including SSD and data disks, and does not share disks with other features.
  • You can have multiple Virtual SAN clusters for each vCenter Server instance.


Characteristics of a Virtual SAN Datastore

  • Virtual SAN creates a single Virtual SAN datastore accessible to all hosts in the cluster, whether or not they have disks. All hosts can also mount any other datastores, VMFS or NFS.
  • If you have multiple Virtual SAN clusters for each vCenter Server, each cluster provides a Virtual SAN datastore. You can use Storage vMotion to move virtual machines between the Virtual SAN datastores.
  • Only HDD disks contribute to the capacity of the datastore. The capacity of SSDs is not counted as part of the datastore as it is used as a read cache / write buffer.
  • In automatic mode, a Virtual SAN datastore dynamically grows when you add hosts to a Virtual SAN cluster, or disks to any cluster member.

Two way to build a vSAN Node

Select a prebuilt Ready Node – Ready Node is a single tested pre-configured server and Ready-Block is a tested pre-configured set of servers for use with Virtual SAN
Select individual components using the Virtual SAN Compatibility guide:

  • Any server on vSphere Hardware Compatibility List
  • Multi-level cell SSD (or better) or PCIe SSD
  • 6Gb enterprise-grade HBA/RAID controller



vSphere Storage Appliance

VMware Virtual SAN

Description Low cost, simple shared storage for small deployments Scale-out distributed storage designed for virtualized/cloud environments
Form factor Virtual Appliance Built-in vSphere kernel
Ideal Targets
•Small SMB
•ROBO deployments
•2 to 3 vSphere servers
•Does not scale beyond 3 hosts


•Minimum 3 hosts deployments
•Scale out to vSphere cluster size
Performance No SSD (low performance) SSD caching (high performance)
•Simple install & configure
•Scales up to ~16TB usable storage
•vCenter-integrated management
•SSD caching and intelligent data placement
•Rapid storage provisioning
•Scale-out for large deployments
•Granular scaling
•Storage policy based management