Test Center: SANs tuned for virtualization pack nice surprises
Compellent, Dell, HP, Pillar Data, and roll-your-own Pillar/DataCore bring strong storage management features to XenServer, VMware, and Hyper-V environments
In addition to creating snapshots on a regular basis to capture changes to VMDK or VHD files, you may want to enable replication, either to another local storage system or to a remote system at another location. Doing this through the storage system rather than via add-on software on the hypervisor can save you quite a bit of money. These features come with many SAN systems (including all of those reviewed here except the HP, which provides snapshots but not replication) and can provide redundancy for multiple virtualization servers with no per-server cost.
Three of the systems -- the Compellent Storage Center, Dell EqualLogic, and Pillar Data Axiom -- integrate with VMware's Site Recovery Manager to automate fail-over to a secondary site; Site Recovery Manager also allows you to automate the testing of your disaster recovery process with these SANs. The Dell EqualLogic system also integrates with the Citrix XenCenter management console to streamline storage provisioning and tasks such as cloning, snapshotting, and resizing virtual disks for XenServer environments.
Roll your own
Ironically, the least expensive system in my test, the Promise/DataCore combination, is also the only one that includes a plug-in for VMware's management clients that allows you to provision, share, clone, replicate, and expand virtual disks among physical servers and VMs. DataCore will also let you try the software for free, as a virtual appliance that can run on Citrix XenServer or Microsoft Hyper-V, working with up to a terabyte of storage.
On the other hand, although DataCore SANmelody offers an extra degree of integration with most virtualization platforms, it may make many administrators nervous. Because SANmelody runs on top of Windows and uses whatever storage the server can see, assembling a high-performance system will require careful planning and research into the most appropriate hardware. If there are problems, there's no single support number; the Promise storage system, the separately purchased hard drives, and the Windows and DataCore software are all supported separately.