Introduction to DataCore Virtual SAN

DataCore Virtual SANs

DataCore™ SANsymphony™-V virtual SAN represents an alternative to external SANs which pools storage devices directly attached to a group of host servers yielding improved application performance and high-availability within a highly-consolidated server infrastructure.

A DataCore virtual SAN can leverage any combination of flash memory, solid state disks (SSD) and magnetic disks to provide persistent storage services as close to the application as possible without having to go out over the wire. Virtual disks provisioned from the virtual SAN can also be shared across a cluster of servers within the server group to support the dynamic migration and failover of applications between nodes.

Ideal Use Cases for DataCore Virtual SANs

Consider the DataCore virtual SAN solution for:

Latency-sensitive applications
Speed up response and throughput by leveraging flash memory as persistent storage close to the applications and caching reads and writes from even faster server DRAM memory.

Small Server Clusters in Remote Sites, Branch Offices and Small Computer Rooms
Put the internal storage capacity of your servers to work as a shared resource while protecting your data against server outages simply by adding SANsymphony-V software.

Virtual Desktop (VDI) Deployment
Run more virtual desktops on each server and scale them out across more servers without the complexity or expense of an elaborate external SAN.

Virtual SAN and Virtual SAN Nodes

A DataCore virtual SAN is comprised of two or more physical x86-64 servers with local storage, hosting applications. Up to a maximum of 32 servers may be configured within a centrally-managed group. Each server participating in the virtual SAN must run a properly licensed instance of SANsymphony-V. These physical servers are also referred to as virtual SAN nodes (or simply nodes). Generally each node contributes storage to the group’s shared pool. You may also configure SANsymphony-V nodes that do not contribute storage to the pool but host applications that access storage from the pool.

Virtual SAN Storage Devices
Uninitialized block storage devices attached to a node (with the exception of its boot drive) can be included in the virtual SAN. Any combination of flash memory, SSD and magnetic disks may be used. Removable USB devices are not supported since they cannot be relied upon to be present.

SANsymphony-V Deployment Options
There are three ways to configure the SANsymphony-V software on the application servers depending on the operating system or server hypervisor controlling the physical machine.

Physical Windows Server (no server hypervisor installed)
SANsymphony-V runs directly on top of the Windows Server operating system. All local block storage devices that are not initialized are automatically detected as suitable for the pool. An application such as Microsoft Exchange or SQL may be installed alongside SANsymphony-V. Windows Failover Cluster or other clustering technology can be used to provide application failover between servers.

Windows Server with Hyper-V
SANsymphony-V runs in the root partition (also referred to as the parent partition) on top of the Windows Server operating system. All local block storage devices that are not initialized are automatically detected as suitable for the pool. The Microsoft Hyper-V hypervisor role is installed alongside SANsymphony-V.

VMware ESXi and other non-Windows based hypervisors
SANsymphony-V runs within a dedicated Windows Server virtual machine. The administrator assigns uninitialized storage devices from the server hypervisor to the SANsymphony-V virtual machine as raw storage devices (RDMs in ESXi). The presentation of raw storage devices is preferred, but may not always be an option based on hypervisor and/or local RAID controller capabilities.

NOTE: All local disk-RDM mapping files being presented to SANsymphony-V must reside on the node’s local datastore (not within a virtual volume presented from SANsymphony-V).

Enterprise SAN Features
SANsymphony-V provides the following enterprise storage features:

  • Automated Storage Tiering
  • Advanced Site Recovery *
  • Analysis and Reporting
  • Asynchronous Replication *
  • Channel Load Balancing
  • Continuous Data Protection (CDP) *
  • Fibre Channel support *
  • High-Speed Caching
  • iSCSI support
  • NAS/SAN (Unified Storage)
  • Snapshot
  • Storage Migration and Pass-through Disks
  • Storage Pooling
  • Synchronous Mirroring
  • Thin Provisioning

(*) Optional Features

Virtual SAN Licensing
A SANsymphony-V license is required per node. Licenses are based on the amount of physical storage the node contributes to the shared pool. Some features are separately priced. Please refer to a DataCore authorized representative for more information regarding licensing and pricing.

Disk Pools
In SANsymphony-V, storage devices are organized into disk pools. You may create multiple disk pools within a virtual SAN node to distinguish how each resource pool will be used. For example, one would create a production disk pool and a test disk pool to separate which storage will be allocated to production and what devices are best suited for testing.

Auto-tiering within Disk Pools
Members of a disk pool may have differences in performance characteristics. SANsymphony-V uses sub-LUN automated storage tiering to dynamically match the best device to a given workload based on how frequently blocks of storage are accessed. This ensures that hotter-data resides on faster disk and cooler-data resides on slower disk within the pool.

Virtual Disks
Thin-provisioned virtual disks created from a node’s disk pool can be shared with other nodes in the virtual SAN. They appear as well-behaved logical drives to the operating systems or hypervisors that they are explicitly served to.

High-Speed Cache
Each virtual SAN node requires some amount of RAM to be used as high-speed cache. The amount of RAM allocated can be modified as necessary, but generally a minimum of 4GB or 10% (whichever is higher) of the host’s total available RAM is recommended for use as high-speed cache.

The purpose of the high-speed cache is to serve as a speed-matching buffer for writes and a large cache for reads. The result is conservatively a 3-5x performance increase over the native performance of magnetic disks. The use of RAM as read-write cache provides a significant performance advantage over virtual SAN products that only use slower flash memory as a read cache device.

Synchronous Mirroring for High Availability
SANsymphony-V provides continuous access to the shared storage pools even when a virtual SAN node is out of service. Critical data is synchronously mirrored between pairs of virtual SAN nodes to achieve high-availability. RAID protection within each node provides additional safeguards against component-level failures.

How the virtual SAN Works

The diagram below shows an example of a virtual SAN. SANsymphony-V (in red) is running in a dedicated virtual machine (VM) on each node alongside VMs hosting applications.

DataCore Virtual SAN
In the diagram above, the left two nodes are responsible for sharing a highly-available virtual disk with the other nodes that make up the group of servers. Each node pools its local flash and magnetic storage devices. Virtual disks are created from these pools and are synchronously mirrored between the two nodes. They are presented as multi-path disk devices over the network/fabric. The virtual disks may be sized as needed. Oversubscribing the storage is allowed since the virtual disks are thin provisioned to minimize actual capacity consumption.

The two left nodes, as well as any of the other virtual SAN nodes in the virtual SAN, can access the virtual disk over the network/fabric. Each node’s corresponding hypervisor recognizes the virtual disk as an available disk device.

In this same way, other nodes can contribute to the overall capacity of the shared storage pool. Each node adds more storage, processing, network and I/O power to the group.


The DataCore™ SANsymphony-V10 virtual SAN software can scale performance to more than 50 Million IOPS and to 32 Petabytes of capacity across a cluster of 32 servers, making it one of the most powerful and scalable systems in the marketplace. To help users evaluate the power of the new Virtual SAN capabilities and further educate themselves on the benefits of software-defined storage, DataCore is providing free access to a non-production use Virtual SAN software license. The free SANsymphony-V10 Virtual SAN software is now available for download at:

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