June 30 2014, mark the date, people. This is the day when VMware announced their public beta of Virtual Volumes. Virtual Volumes, or VVOL as VMware likes to call them, put a Virtual Machine and its disks, rather than a LUN, into the storage management spotlight. Through a specific API, vSphere APIs for Storage Awareness (VASA), your storage array becomes aware of Virtual Machines and their Virtual Disks. VASA allows to offload certain Virtual Machine operations such as snapshotting and cloning to the (physical) storage array.
Now, what is the big deal with Virtual Volumes, VMware? Open vStorage has been designed to allow administrators to manage each disk of a Virtual Machine individually from day one. We don’t call it Virtual Volumes but call it VM-centric, just like anyone else in storageland does. VMware, don’t get me wrong, I applaud that you are validating the VM-centric approach of software-defined storage solutions like Open vStorage. For over 4 years, the Open vStorage team has worked at creating a VM-centric storage solution which supports multiple hypervisors such as VMware ESXi and KVM but also many backends. It is nice to see that the view we had back then is now validated by a leader in the virtualization industry.
What confuses me a bit is that while the whole world is moving towards shifting storage functionality into software, that you take the bold, opposite approach and push VM-centric functionality towards the hardware. This behavior is strange as everyone else is taking functionality out of the legacy storage arrays and is more and more treating storage as a bunch of disk managed by intelligent software. If I remember it correctly, you declared at VMworld 2013 a storage array to be something of the past by announcing VSAN. The fact that storage arrays are according to most people past their expiry date was recently confirmed by another IT behemoth, Dell, by OEM-ing a well-known hyperconverged storage appliance.
A said before, Open vStorage has been designed with VM-centric functionality across hypervisor flavors in mind. This means that taking a snapshot or cloning a single Virtual Machine is as easy as clicking a button. Being a VM-centric solution doesn’t stop there. One of the most important features is replication on a per Virtual Machine basis. Before implementing this critical feature, the Open vStorage team has had a lot of discussion about where the replication functionality should be in the stack. We could have taken a short-cut and pushed the replication back to the storage backend (or storage array as VMware calls it). Swift and Ceph for example have replication as their middle name and can replicate data across multiple locations worldwide. But, by moving the replication functionality towards the storage backend you lose your VM-awareness. Pushing functionality towards the storage array is not the solution, intelligent storage software is the only answer to a VM-centric future.