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One of the big benefits of hyper-converged infrastructure is simplicity. But hyper-converged vendors offer a range of various node models with different hardware, and that makes it difficult for some organizations to choose the right platform for their workload.
Some HCI vendors only have a small number of appliance models; others have a wide range. Depending on your workload, you might have very specific requirements for the hardware configuration of your HCI nodes. Let's explore three workload types and which HCI appliance options might best support them.
Types of workloads
One of the first workloads for HCI was virtual desktop infrastructure (VDI). VDI tends to have a higher CPU load than server virtualization and requires higher storage performance. Since VDI tends to have built-in storage efficiency and responds well to deduplication, capacity is not usually a problem.
A good HCI node for VDI has about 256 GB of RAM and medium core count CPUs. There will be a lot of VMs in this environment, and it's likely you will overcommit CPUs and possibly RAM because not all of the desktops will be active at the same time. Ideally, the storage is a low-capacity, all-flash configuration for high performance without excessive cost.
A general-purpose server virtualization platform might hold all of the Windows and Linux servers in your data center. This is likely a RAM-heavy workload, and you will need to use the backup features of an HCI appliance. So, storage capacity is critical. Medium core count CPUs are ideal and, depending on the price of RAM, around 512 GB of RAM per node. To get enough storage capacity without a high cost, use a hybrid storage configuration -- including some solid-state drives (SSDs) for performance and plenty of hard drives for capacity, particularly backup capacity.
A more complex, high-performance application, such as an SAP environment, will include a few database servers, which demand a lot of RAM and high-performance storage. The remaining application servers require less storage performance but a lot of RAM and CPU.
This workload type requires an HCI node with about a terabyte of RAM and high core count CPUs. In this case, you will not overcommit physical CPUs or RAM. To optimize database performance, use all-flash. It's possible that you won't use the HCI's backup features. Instead, you can deploy the database and application servers in a high availability configuration and send backups to another platform, such as a virtual tape library.
HCI appliance vendor options
One early HCI appliance vendor was Nutanix, with its four nodes in 2U NX-3000 series box. Today, Nutanix has an overwhelming amount of options to choose from. This is likely because Nutanix has been in the market for a while now. So, many of their customers have requested different configurations.
The current release of the platform has five different CPU options with between 16 to 36 cores per node. There are six options for RAM with between 128 GB and 1.5 TB. There are also six options for SSD size and two for hard disk and a choice between all-flash or hybrid storage. There are three series nodes to choose from in the Nutanix lineup: 1000 series, 6000 series and 8000 series.
Dell/EMC's VxRail is based on vSphere and vSAN. There are five different series of node types, each with a range of CPU, RAM and storage options.
Hewlett Packard Enterprise (HPE) acquired SimpliVity in January 2017. The acquisition gives HPE a place at the hyper-converged table. The new SimpliVity nodes are all based on HPE's DL380 servers and are only available as all-flash configurations. Over time, some of HPE's denser form factors might offer SimpliVity. For now, the only option is a 2U server. The inherent data efficiency of SimpliVity makes the effective storage capacity far greater than the native capacity listed here.
Match platform to workload
In an HCI design, it's important to select a node configuration that matches the demands of your workload. When you specify your HCI nodes, keep in mind that the storage cluster function will consume some of the resources. Whether it's as noticeable as a virtual SAN appliance configuration, or simply resources used by the hypervisor, you'll have to pay for extra resources if you don't have a separate storage array. Some HCI appliance vendors are also software-only, allowing you to choose from any hardware that your hypervisor supports.
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