Storage only Nutanix nodes have now been available for over a year now, and have seen great adoption with Nutanix customers looking to solve the issue of an ever increasing storage footprint.
This solves one of the false arguments that some people have against hyper-converged infrastructure stating that it is required to scale compute at the same time as storage. Not the case with Nutanix. The storage only nodes run Acropolis Hypervisor (AHV) with a single CVM to form the storage pool, so do not require separate vSphere licencing.
Adding storage nodes are simple. Simply connect them to the Network, power them on, wait for them to be auto discovered, add IP addresses, then click expand in Nutanix Prism. The storage container presented to vSphere via NFS is then automatically extended with no downtime. No knowledge of KVM is required as the Storage Only nodes are managed via Nutanix Prism. Much less complex than expanding a legacy storage array by adding disk shelves and carving out new LUNS.
One of the new announcements amoung many others that came out of the Nutanix .NEXT 2016 conference in Las Vegas was the ability to convert any Nutanix Nodes to Storage Only. This functionality is expected to be released in a future Nutanix software update around October of 2016. My colleague Josh Odgers gives a good overview of this capability on his blog here http://www.joshodgers.com/2016/06/15/whats-next-2016-any-node-can-be-storage-only/
An interesting scenario you could do with this capability would be to convert your old existing Nutanix nodes to storage only when you are ready for an expansion of your existing Nutanix infrastructure. Since Intel CPU’s get much faster during new release cycles and also support larger amounts of memory, this allows you to potentially decrease vSphere cluster sizes and run even more VM’s on less hardware without needing to reduce storage capacity. Since the Storage only nodes still run a CVM that is part of the Nutanix cluster, there is no loss in overall cluster resiliency and this will also allow you to explore enabling new functionality such as Erasure coding (ECX) to your cluster.
Converting nodes to storage only also has the distinct advantage of not mixing a vSphere cluster with non-homogenous nodes with different CPU generations and RAM capacity. Whilst this is supported via VMware EVC, it is not always ideal if you want consistent memory capacity and CPU performance across your vSphere cluster. EVC will need to mask some newer CPU features which could cause a decrease in performance. Also VMware HA will also need some careful calculations to ensure there is enough capacity in your cluster if one of the larger hosts fails.
A good example of converting nodes to storage only would be if you had previously purchased a cluster of NX-6020 nodes which were orginally designed for storage heavy applications that do not require much compute capacity
The NX-6020 was released back in 2013 with the following per node specifications
Dual Intel Ivy Bridge E5-2630v2
[12 cores / 2.6 GHz]
1x 800GB SSD
5x 4TB HDD
Now say you had purchased a cluster of four of these models, and are running ESXi as your hypervisor. The cluster was purchased in 2014 with a five year warranty for the purpose of virtualizing an Email Archiving application, that is typically a low IOP’s high storage capacity workload.
After the initial success of virtualizing this application you decide to migrate some more compute and memory heavy workloads, so decide to go with four NX-3060-G5 node’s with the following specifications
Duel Intel Broadwell E5-2680v4
[28 cores / 2.4 GHz]
2x 800GB SSD
4x 2TB HDD
With this new purchase, you have the following options for Expansion. Nutanix supports adding hosts of different capacity to the same cluster.
- Add the new nodes to the Existing Nutanix Cluster, and existing vSphere Cluster for a total vSphere cluster size of 8 hosts with varying RAM and CPU sizes. EVC will need to be enabled at the Ivy Bridge generation.
- Add the new nodes to the Existing Nutanix Cluster, and create a new vSphere cluster of four hosts. You will have two vSphere clusters consisting of a total of 8 hosts.
- Add the new nodes to the Existing Nutanix Cluster. Create a new vSphere cluster and vMotion VM’s to this cluster. Convert old nodes to storage only. You will have a single vSphere cluster consisting of four hosts of more CPU and RAM capacity than was available on the NX-6020, whilst still re-using your existing storage.
The following grapths show the perfomance and capacity differences between four nodes of NX-6020 vs four nodes of NX-3060-G5. The CPU performance alone is almost three times the capacity when you look at the Combined Spec Int Rating of the CPU’s. The Ivy Bridge CPU’s have a spec-int rating of 442 per node whilst the new broadwell cpu’s have a spec-int rating of 1301. As the new nodes are compute heavy, the NX-6020 nodes have more storage capacity due to utilising larger 4TB 3.5inch drives.
During sizing calculations you determine you can easily fit the new workloads along with the existing email archiving application on a single vSphere cluster of four nodes, whist the existing NX-6020 cluster has been converted to serve storage only to the cluster. This will give us a total usable capacity of 52.16 TB as you can see in the following diagram. Sizing has been done using http://designbrewz.com/ and shows usable, not RAW capacity.
But wait, theres more! Since the Nutanix Cluster has been upgraded from four nodes to eight, you also decide to now enable Erasure Coding on the cluster for even more capacity savings. Whilst this is supported on four nodes with a 2/1 stripe size, it is recommended to be used on larger Nutanix Clusters of more than six nodes, to take advantage of a 4/1 stripe size. With Erasure Coding Enabled, our usable capacity has now increased from 52.16TB to 83.45TB, calculated at 1.25x RAW capacity overhead for RF2+ECX vs 2x for RF2 only.
So what have we gained with this addition of four NX-3060-G5 nodes and converting our old nodes to storage only?
- vSphere Licencing costs have stayed exactly the same with the addition of new Hardware.
- Our RAM capacity has increased by four times by upgrading each node from 128GB to 512GB
- Our CPU Capacity has tripled, whilst the socket count is the same.
- Our storage capacity has more than doubled even though we added compute heavy nodes, by taking advantage of erasure coding delivered entirely in software
- Cluster resilency and performance has increased by increasing CVM’s from four to eight
- Rack Space has only increased by 2RU in the datacentrer
Not a bad result, and really show’s the advantages you gain by running software defined infrastructure that increases value and ROI purely via software updates throughout it’s lifecycle.