SAN and Compute All-In-One
Let’s be honest, x86-based compute in virtualization environments is pretty darn boring. A server has become the necessary evil required for enabling the coolness that is virtualization.
But, don’t let the boringness of servers fool you. VMware has enabled a new breed of hybrid servers that are both server AND storage all-in-one! This new paradigm adds some new methods and models for virtualization design and functionality.
Conceptually, the server boots into an ESXi environment and fires up a guest OS. This guest OS is the virtual storage appliance and provides the storage for the local server. The guest makes use of VMDirectPath functionality to take control of a locally installed storage controller connected to the local disks. The result of this is that the VM can access the local disks and ESXi will not. The local disk is now directly connected to the VM. How cool is that?!
Once the guest OS has the disks, the guest creates various storage options: block or file, object or RAID, etc…). The ESX host is, then, configured to connect to IP storage provided by the guest. The first, typical reaction may be to wonder about the reason to add this level of complexity. For a standalone host with local storage (think ROBO) this may be a little overkill. But, the advantage comes into play when you consider flexibility and new functionality.
By moving control of local storage into the VM, more advanced functions can be performed. Local storage use by ESXi is fairly limited. The VSA, though, can use the storage a little more liberally.
Take Pivot3, for example. Their VDI and surveillance solutions make use of this storage technique. The vSTAC OS (the Pivot3 VSA) creates a RAID across the local disks. Yawn, right?! Where the coolness is applied is when multiple nodes are "connected". vSTAC OS instances on other Pivot3 servers combine and RAID across multiple hosts. Suddenly, local storage is combined with local storage from other hosts and creates a big clustered pool of available storage! This cluster environment allows for added resiliency and performance as the data is no longer restricted to the local host and distributed to help against local storage issue.
Once the vSTAC OS nodes connect their storage together, data is spread across all of the other nodes to immediately protect the data and enhance performance. A new node can be added in the future. Once the new node is added, the data is automatically rebalanced across all hosts to ensure proper protection and efficient usage of the storage. Dynamic add of storage and compute is fantastic!
The VSA VM can perform additional functions if desired (and developed as such) like: deduplication, replication, compression, etc…
I love this type of innovation. There are many use cases for solutions like this. The Pivot3 solution has a lot of potential for success in their target markets. I have concern about the selection of RAID versus object storage, though… but that is their decision. Traditional RAID5 systems suffer heavily from a disk failure and rebuild… the performance tanks until the failed disk has been replaced. In the event of a failure in the Pivot3 solution, the entire solution may suffer until the offending disk has been replace. But, with that said, I believe the benefits of the technique outweigh the potential performance hit.
This style architecture really bucks the trend of needing a separate SAN/NAS in addition to compute. Adding sophistication to the VSA component and introducing more SSD/Flash-based storage could create an interesting and valid competitor to traditional SAN/NAS solutions and breathes new life into boring servers.