Most of you have seen the announcement around Virsto by now, for those who haven’t read this blog post: VMware to acquire Virsto. Virsto is a storage company which offers a virtual storage solution. I bumped in to Virsto various times in the past and around VMworld 2012 got reminded about them when Cormac Hogan wrote an excellent article about what they have to offer for VMware customers. (Credits go to Cormac for the detailed info in this post) When visiting Virsto’s website there is one thing that stands out and that is “software defined storage”. Lets take a look at what Virsto offers and what software defined storage means to them.
Lets first start with the architecture. Virsto has developed an appliance and a host level service which together forms an abstraction layer for existing storage devices. In other words, storage devices are connected directly to the Virsto appliance and Virsto aggregates these devices in to a large storage pool. This pool is in its turn served up to your environment as an NFS datastore. Now I can hear you think, what is so special about this?
As Virsto has abstracted storage and raw device are connected to their appliance they control the on-disk format. What does this mean? Devices that are attached to the Virsto appliance are not formatted with VMFS. Rather Virsto has developed their own filesystem which is highly scalable and what makes this solution really interesting. This filesystem is what allows Virsto to offer specific data services, to increase performance and scale and reduce storage capacity consumption.
Lets start with performance, as Virsto sits in between your storage device and your host they can do certain things to your IO. Not only does Virsto increase read performance, but their product also increases write performance. Customers have experienced performance increases between 5x and 10x. For the exact technical details read Cormac’s article. For now let me say that they sequentialise IO in a smart way and de-stage writes to allow for a more contiguous IO flow to your storage device. As you can imagine, this also means that the IO utilisation of your storage device can and probably will go down.
From an efficiency perspective Virsto optimizes your storage capacity by provisioning every single virtual disk as a thin disk. However, this thin disk does not introduce the traditional performance overhead associated with thin disks preventing the waste of precious disk space just to avoid performance penalties. What about functionality like snapshotting and cloning, this must introduce overhead and slow things down is what I can hear you think… Again, Virsto has done an excellent job of reducing overhead and optimizing for scale and performance. Virsto allows for hundreds, if not thousands, of clones of a gold master without sacrificing performance while saving storage capacity. Not surprising Virsto is often used in Virtual Desktop and large Test and Development environments as it has proven to reduce the cost of storage with as much as 70%.
Personally I am excited about what Virsto has to offer and what they have managed to achieve in a relatively short time frame. The solution they have developed, and especially their data services framework promises a lot for the future. Hopefully I will have time on my hands soon to play with their product and provide you with more insights and experience.