HCI Benefits without HCI, Part 2: Policy

Hyperconverged infrastructure (HCI) is having a significant impact in data centers around the world. Many IT organizations are getting a lot of benefits from a VM-centered approach to infrastructure. I don’t think that an HCI product is necessary to get these benefits. Most of the benefits of HCI could be delivered by software on top of older architectures. The big HCI benefits I see are:

  1. Modular, scale-out expansion
  2. No dedicated storage network, no Fibre Channel
  3. Simplified management

In a previous article, I looked at the first two, which are both about the physical aspects of hyperconverged infrastructure. Today, I am going to address the third point, which I think is the biggest benefit of HCI.

Simplified Management

Simplified management is where I think hyperconverged infrastructure ends up being most valuable to customers. Deploying HCI means not having to concern yourself with managing all the things beneath the hypervisor. You get more time for looking after applications and end users. One element is the simplification of managing physical components, and the other is the use of policy to manage VMs.

Storage Management

Storage management is the first thing to be simplified by HCI; the platform handles the hard parts of storage management. There is usually a simple storage management interface, which is centered on VMs and the needs of those VMs. Most often, the storage management is done by applying policies to groups of VMs. The storage policies usually cover three core areas:

  1. Storage availability
    • How many failures from the underlying storage infrastructure can a VM tolerate?
    • This policy drives the RAID or erasure coding configuration underneath the VM
  2. Storage performance
    • May drive or prioritize the use of SSD
    • May drive the spreading of the VM data across many disk spindles
  3. Backup and replication
    • Scheduled local recovery points, storage snapshots
    • Scheduled remote recovery points, replication

These policies remove the need to manually configure storage. The HCI platform handles any LUNs, file shares, RAID, snapshots, replication, and retention. There is nothing inherent to HCI that enables VM-centered, policy-based storage management.

I believe that the only way to work with large numbers of VMs is by using policy for management, rather than direct manipulation of settings. HCI vendors follow this approach, with policies that are applied to VMs. Performance, availability, and DR are all policy elements for VMs. With some legacy storage technologies, these aspects are all derived from the LUN or share on which the VM resides. To change the DR stance on a VM, it is migrated from a LUN that is not replicated to one that is replicated. With an HCI product, the VM is assigned the policy that it be replicated to the DR site. Policy is applied to the VM, and the infrastructure does whatever it needs to fulfill the policy. Older products could be wrapped in more smart software to deliver this policy-based management. There is nothing inherent in the HCI architecture that makes this possible.

Simplified management has become a core value for most modern storage systems. VMware has been pushing policy-based storage management, which is core to HCI. VMware has also helped us with VVols, which remove the reliance on datastores and LUNs. Many parts of policy-based management are entirely possible without HCI. Storage systems are getting simpler to manage, and many have plugins for vSphere. The vSphere plugins can reduce the need to manage as many aspects of the storage system.

Hardware Management

One of the difficult tasks in managing infrastructure is the interdependent complexity of that infrastructure. There is a complex matrix of compatibility between versions of the hypervisor, storage adapter drivers and firmware, network adapter drivers and firmware, physical switch configurations, and storage system firmware and configuration. Keeping all these elements in a supported and optimally configured collection is a tough job. Both converged and hyperconverged should help to reduce the number of elements and simplify keeping everything in sync. The Nutanix “one click upgrade” is a great example of a simple mechanism to keep everything in an optimal state. HCI and CI achieve this simplicity in part by restricting hardware choice. Therefore, many HCI products are software wrapped up in hardware. We are starting to see tools, like Runecast, that provide visibility into the issue of compatibility and configuration best practices. Using vendor builds of your hypervisor also helps ensure a consistent set of drivers and firmware for specific hardware.

Many of the benefits of HCI can be delivered by layering software on top of existing architectures. Some vendors have released HCI products that are a mashup of older products and new software. Many vendors have not been able to deliver the kind of simplicity that HCI brings. Maybe they will soon.



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