Compellent Storage Center 4.0

The system I received for testing included a storage controller and two shelves of drives, a tier-one high performance set with sixteen 300GB 15,000rpm drives, and a tier-three high capacity set with eight 500GB SATA drives (and room for eight more), for a total usable capacity of just over 8.5TB. All three boxes included dual controllers and dual power supplies for a fully redundant, dual path 4Gbps Fibre Channel system. The system included all software options: server instant replay (snapshots), dynamic capacity (thin provisioning), data progression (automatic migration of data to lower tiers), and synchronous and asynchronous replication. The as tested price of £43,000 is the second highest in this test, but not exorbitant for what you get.

Creating volumes through the browser based admin console is simple and straightforward, and the virtualisation specific task of coalescing a number of snapshots into a new volume took less than 10 seconds for a 100GB volume. Setting up replication, even to a remote system at another location, is also a snap. The automatic migration of data to lower tiers ensures that the highest performance drives do the heavy lifting, while data that isn't used regularly is migrated to less expensive SATA storage. The system offered eight 4Gbps Fibre Channel connections, enough to support multiple VMware servers with sixteen or more VMs per server without storage bottlenecks.

Compellent also includes a full PowerShell plugin command set for both Hyper-V and VMware environments. PowerShell, the scripting tool included with Windows Server 2008, allows for easy automation of tasks from Windows systems. The plugin allows an admin to script tasks such as provisioning LUNs and volumes, configuring LUN masking, formatting volumes, installing VMs through Hyper-V Manager or VMware's Virtual Center (or vCenter Server), and installing images - pretty much all the tasks you might want to automate when provisioning storage along with a virtual environment. The system supports full interaction with PowerShell to pull information on available volumes and perform error checking. This requires some basic programming, but still allows for complete provisioning of both Hyper-V and VMware VMs, as well as their storage, through one interface.

Compellent has another unique feature: the white space recovery tool. Windows' NTFS is constructed to write new files to any unused blocks on disk before writing over blocks that have been freed up by deleting files. This doesn't matter on a normal hard disk, but will cause thin provisioned virtual volumes to quickly expand to their maximum capacity. Compellent's recovery tool searches for blocks that are part of deleted files and marks them as unused so that Windows will overwrite them rather than using up all available space, thus ensuring that volumes don't expand unnecessarily.