After months of beta testing boasting 12,000+ beta testers, VMware has finally thrown its hat into the hyperconverged virtualization space with the GA release of VMware vSphere 5.5 Update 1. Among numerous bug fixes to vSphere, this release contains the GA code for VMware VSAN. VSAN is a shared-nothing clustered storage technology embedded in the vSphere hypervisor, ESXi, that uses collections of local, direct-attached host storage to provide reliable and high-performing storage to a vSphere cluster. It relies on both traditional rotating disk media and modern flash and solid-state drive (SSD) storage, forming clusters of up to 32 ESXi hosts over 1 Gbps or, preferably, 10 Gbps network connections.
VMware boasts that VSAN, its current primary entry in the software-defined storage area, can scale linearly to 2 million IOPS, 4.4 petabytes, and 3,200 VMs across 32 physical hosts while reducing total cost of ownership by 50%. It does this through a number of techniques. First, VMware claims it is a two-click install, mostly because the software is shipped as a part of ESXi and it discounts the time for hardware setup, which can be considerable in an established environment. It is managed through the traditional vSphere interfaces, lending familiarity to the process of storage management and eliminating the requirement for IT staff to possess specialized skill sets. VSAN also does away with much of the traditional storage configuration and operations work, as there are no LUNs to provision, VM provisioning happens through the storage policy engine within vSphere 5.5, and VSAN is self-tuning once operational.
VSAN requires at least three hosts to begin, each host having at least one supported solid-state drive (SSD), one supported traditional disk, and a supported disk controller, with the SSD having at least 10% of the capacity of the traditional disk. Customers can build their own VSAN hardware or purchase preconfigured VSAN-ready nodes from Cisco, Dell, Fujitsu, IBM, and SuperMicro beginning in April. Though it is recommended, not every node in a VSAN-capable cluster needs to have storage; however, every node does need to be licensed. VSAN is licensed per CPU socket, with list prices beginning at $2,495 per socket, or $50 per user in a Horizon View virtual desktop environment, not including ongoing service and support. Promotional bundles are available for previous users of the VMware Virtual Storage Appliance (VSA), customers looking to add vSphere Data Protection Advanced, and beta test participants.
VSAN supports up to 3,200 VMs, which is actually a limit of 100 VMs per host. VDI implementations will often exceed 100 virtual desktops per physical server, and since the licensing model favors larger physical hosts, the 100 VM limit is likely to be seen by customers less as a technical limitation than a way to force additional sales. Under the hood, VSAN is an object data store that just happens to look like a normal vSphere datastore, and there are also limits on the number of objects that can be present. Snapshots, configuration files, and virtual disks all count as objects, toward the limits, which are worth exploring if you have virtual machines with more than a few of any of those. VSAN also continues the age-old 2 TB limits on virtual disk files, which were lifted to 62 TB for traditional storage datastores when vSphere 5.5 shipped. These limits, plus the per-socket pricing, makes casual use of VSAN unlikely and eliminates as possible customers many enterprises with blades or other converged infrastructure with limited physical storage capacity.
Most 1.0 products from VMware live up to the adage that says perfect is the enemy of done. VSAN is far from perfect, but for it to get better it needs to ship to customers. It is also far from alone in making many of these promises to customers. Arrays from Tintri, Coho Data, Tegile, and others offer LUN-free operation, deep virtualization integration, policy-based management, drastically lower TCO, and linear scale-out with their standards-based IP storage solutions. However, for controlled use cases such as disaster recovery sites, well-considered cases like VDI, and many greenfield deployments in general, VSAN presents an attractive, easy to manage, easy to scale storage offering that leverages the IP networking connectivity you have or were installing anyway.
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