What would appeal to you more: redundant storage controllers or replicated storage?
Last week Synology launched its new RC18015XS+ server storage platform. In high availability scenarios, rather than requiring a full replica of both the storage and the controller, the platform allows multiple redundant controllers to access the same shared pool of storage. If the "active" controller has an issue, the "passive" controller takes over.
There's an obvious benefit in cost terms: not having to set up a replica storage pool means you don't have to duplicate all that disk space and associated hardware. The trade-off is that you'll have a potential single point of failure: if there's a catastrophic event with your storage pool (such as lack of power, rather than just an individual drive failure), then neither controller will be able to do anything useful.
Experience suggests that may not be a make-or-break issue, however. High availability is important, but in most cases it's the controller and the network that matters," Steven Gordon, technical solutions administrator for The Digital Foundry, told Lifehacker at the launch.