Monday, July 19, 2010

As we discussed in our recent article “The Complexity of VMware Storage Management,” there are plenty of challenges involved when trying to manage VMware storage, including unpredictability in the environment and the need to run resources at ever-higher utilization rates. What do you do when storage I/O bandwidth needs or storage capacity requirements surge unpredictably? You can’t simply just stand up another storage system. Even if there was the budget, the time to order, receive and integrate that system into the virtual infrastructure would take far too long and be too disruptive.

Planning is key. Before a peak requirement hits you, look at your current storage infrastructure. Will it handle a sudden need for additional capacity or I/O? Some storage vendors have gotten better at adding additional shelves of storage to a storage system but how hard is it to let the environment know that it has more storage available to use? Scale-out storage has one of the simplest capacity addition processes. Simply connect in another node and the capacity is instantly available. Like Lego blocks.

The challenge with adding capacity in the virtual environment is that there are more layers in a virtual infrastructure; the storage system, the virtual file system and the virtual machine image. When capacity is added each layer needs to understand that it has more capacity available to it. Does your storage system and the chosen protocol (Fibre, iSCSI or NFS) handle that or does each volume and then virtual machine on those volumes need to be touched and have its capacity expanded? Scale-out storage, especially when configured to present VMware images with a NAS protocol, automatically insures that each layer understands that capacity has been added.

I/O is another challenge all together. Unlike capacity most storage systems are not designed to add additional I/O capacity. You pay for the I/O upfront whether you need it or not. This means you have I/O resources sitting around idle. Congratulations! When you do eventually consume those resources and need more storage I/O or capacity you can either add an additional unit or upgrade the current one. Both choices are costly and can add to an already complex situation. Scale-out storage is different. Every time capacity is added to the environment, so is I/O bandwidth. The system gets faster with each capacity upgrade, not slower. Even if just I/O is needed most scale-out storage systems have the ability to add just I/O nodes to their systems.

The important value-add in both the capacity and I/O upgrade is that with scale-out storage it is simply a matter of connecting an additional unit. The added capacity and I/O are instantly available to the entire storage system. No manual configuration or individual VM fine-tuning. The virtual environment brings enough variables to contend with but dealing with the unpredictability of storage does not need to be one of them.

George Crump, Senior Analyst