Tag Archives: HCI

Hyper-Converged Cynicism

Or “How I’ve come to love my vSAN Ready Nodes”

I’ll admit it, some years ago I was very cynical about HyperConverged Infrastructure (HCI). Outside of VDI workloads I couldn’t see how it would fit in my environment – and this was all down to the scaling model.

With the building-block architecture of HCI; storage, compute, and memory are all expanded in a linear fashion. Adding an extra host to the cluster to expand the storage capacity also increases the available memory and CPU in the pool of resources. But my workloads were varied, one day we might get a new storage-intensive application, the next week it might be one which is memory intensive. I was used to independently expanding the storage through a SAN and just the compute/memory side through the servers and didn’t want to be either running up against a capacity wall or purchasing unnecessary compute just to cater for storage demands.

This opinion changed when my own HCI journey started in 2017 with the purchase of a VMware vSAN cluster built on Dell Ready Nodes. Whist I’ll be writing about that particular technology here, the principles apply to other HCI infrastructures.



If the problem of HCI could is scaling, the solution is scale. These imbalances in load and growth balance out once a number of VMs are on the system- and this scale doesn’t have to be massive, even from the 4-host starting point of a vSAN cluster I found that when the time came to install node 5, the demands on storage and memory were roughly matched to the relevant capacities of the new node.

The original hosts need to be sized correctly, but unless you’re starting in a totally greenfield environment then you will have existing hosts and storage to interrogate and establish a baseline on current usage requirements. Use these figures, allow appropriate headroom for growth, and then add a bit more (particularly when considering the storage) to prevent the new infrastructure from running near capacity. Remember you are trading a certain level of efficiency for resilience – the cluster needs to be able to withstand at least one host loss and still have plenty of capacity for manoeuvre.

If you are going down the vSAN route, I can thoroughly recommend the ReadyNode option. Knowing that hardware will arrive and just work with the software-defined storage layer without spending hours digging in the Hardware Compatibility Lists was a great time saver, and we’re confident that we can turn round to our vendors and say “this didn’t work” without getting told “it’s because you’ve got disk controller chipset X and that’s not compatible with driver Y on version Z”. There’s a reason I named this blog “IT Should Just Work”.DellEMC vSAN ReadyNode

When expanding the cluster I consider best practice to be to expand with hosts of as similar configuration as possible to the original. If larger nodes are added (for example, storage/memory/CPU is now cheaper/bigger/faster) then these can create a performance imbalance in the cluster. For example a process running on host A might get access to a 2.2GHz CPU, but run the same process on host B with a 3GHz CPU and it will finish slower. Also worth considering is what happens when a host fails, or is taken into maintenance mode for patching. If this host is larger than it’s compatriots then (without very careful planning and capacity management) there might not be sufficient capacity on the remaining hosts to keep the workloads running smoothly.

It is possible in vSAN to add “storage-only” nodes, reducing the memory and possibly going single-socket (this saves on your license cost too!) and then using DRS rules to keep VMs off the host. Likewise “compute-only” nodes are possible, where the host doesn’t contribute any storage to the cluster. Whilst there are probably specific use-cases for both these types of nodes, the vast majority of the time I believe them to be best avoided. Without very careful consideration of workloads and operational practices these could easily land you in hot water.

So, I’m a convert. Two years down the line here and HCI is the on-premises infrastructure I’d recommend to anyone who asks. And those clouds gathering on the horizon? Well, if you migrate to VMware Cloud on AWS then you’re going to be running vSAN HCI there too!

VMworld 2018 Banner

vSAN Scalable File Services

One of the new developments that caught my eye at VMworld this year was the introduction of file services to the VMware vSAN software-defined storage platform. vSAN already offers VMDK storage to vSphere and the ability to host iSCSI volumes, but this feature will allow NFS and SMB file-shares to be hosted directly on the cluster without the need for a separate Windows Server or NFS provider.

What

Yanbing Lee and Duncan Epping discuss vSAN at VMworld Europe 2018

Yanbing Lee and Duncan Epping discuss vSAN at VMworld Europe 2018

vSAN Scalable File Services is a layer that sits on top of vSAN to provide SMB, NFS (and others in future) file shares. It’s comprised of a vSAN Distributed File System (vDFS) which provides the underlying scalable filesystem by aggregating vSAN objects, a Storage Services Platform which provides resilient file server end points, and a control plane for deployment and management.

File shares are created using the vCenter GUI or via API calls from an automation platform, and the demos at VMworld included all the functionality you’d expect with permissions, quotas and so on.

An interesting point is that all the file shares are integrated into the existing vSAN Storage Policy Based Management, and on a per-share basis. Therefore FTT, encryption,  thin provisioning, and so on can all be defined at a pretty granular level. So if only one of your file-shares has an encryption requirement that’s just a case of setting the policy in a drop down list, or likewise if a particular file-share must be configured to be site-failure resilient across a stretched cluster.

Why

Why would you want to do this? Well, a couple of use cases immediately sprang to mind. Firstly, the small office/ remote office/ branch office scenario. A company wants to host both virtual machines and file services in a compact environment- currently the choice would be to have a NAS plus compute hosts, or possibly go hyper-converged but run a VM within this serving the file data from a VMDK. vSAN file services simplifies this by providing that NFS/SMB provision from within the hypervisor- and this also means that all the benefits of resilience, deduplication, compression, and encryption can be provided to the file services.

The second case was for a SAN replacement- a traditional SAN is basically an expandable cluster of x86 servers loaded with disks running some file+disk management software. vSAN is the same thing, but can also run VM workloads. It would be an interesting price/feature comparison exercise to compare the two methodologies.

When

This offering is currently in Public Beta – details at the bottom of this article. NFS 4.1 with AD Authentication is expected at release, with SMB, OpenLDAP, vSAN Data Protection and other functionality to follow. Obviously this is all subject to change as VMware are still at the Beta stage, and a release date has not yet been confirmed.

Further Information

  • HCI3041BE – VMworld Europe 2018 session: Introducing Scalable File Storage on vSAN with Native File Services (Video and Slides)
  • HCI3728KE – VMworld Europe 2018 session:  Innovating Beyond HCI: How VMware is Driving the Next Data Center Revolution (Video)
  • www.vmware.com/go/vsan-beta – Sign up for the Beta. Phase 2 includes the ability to test vSAN File Services in your own lab environment.

VMworld Europe 2018

VMworld 2018 US: HCI1469BU- The Future of vSAN and Hyperconverged Infrastructure

This “HCI Futures” session at VMworld US was hosted by two VPs from the Storage and Availability Business Unit, plus a customer guest. It covered the new features recently added to the vSAN environment with the release of 6.7 Update 1, alongside discussion of the possible future direction of VMware in the Hyper-Converged Infrastructure space. I caught up with the session via the online recording.

HCI is a rapidly growing architecture, with both industry wide figures from IDC and VMware’s own figures seeing massive spending increases. In the week of this VMworld, the 4-year old vSAN product is now boasting 15,000 customers. We are told customers are embarking on journeys into the Hybrid Cloud and looking for operational consistency between their On-Premises and Public Cloud environments.

The customer story incorporated into this breakout session was provided by Honeywell. They were an early adopter of vSAN in 2014, starting with the low-risk option of  hosting their management cluster on the technology. Since then they have replaced much of their traditional SAN infrastructure and are now boasting 1.7 Petabytes of data on vSAN, with compression and de-duplication giving them savings of nearly 700TB of disk.

VMware is pushing along several paths to enhance the product- the most obvious is including new storage technologies as they become available. All-flash vSAN is now commonplace, with SSDs replacing traditional spinning disk in the capacity tiers. Looking to the future, the session talked of the usage of NVMe and Persistent Memory (PMEM) developments – storage latency becoming significantly less than network latency for the first time. This prompts a move away from the current 2-tier model to one which incorporates “Adaptive Tiering” to make best use of the different storage components available.

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In the Public Cloud- in particular the VMware on AWS offering- there have been customers who want to expand storage faster than compute. In the current model this hasn’t been possible due to the fixed-capacity building blocks that HCI is known for. This is being addressed by adding access to Amazon’s Elastic Block Storage (EBS) in 6.7U1 as a storage target for the environment. vSAN Encryption using the Amazon KMS is also included, along with the ability to utilise the Elastic DRS features when using AWS as a DRaaS provider for a vSphere environment.

vSAN is also moving away from it’s position as “just” the storage for Virtual Machines. Future developments include the introduction of file storage- and the ability to do some advanced data management- classifying, searching, and filtering the data.

With all this data being stored, VMware is looking to enhance the data protection functionality in the platform. Incorporation of native snapshots with replication to secondary storage (and cloud) for DR purposes increase the challenge to “traditional” storage vendors- and although it was played down in this talk also encroach further into the backup space which is populated by a large group of VMware partners.

Cloud Native applications are also being catered for with Kubernetes integration- using application-level hooks to leverage snapshots, replication, encryption, and backups all through the existing vCenter interface.

If you want to watch the recording of this session to get more information it’s available on the VMworld site: https://videos.vmworld.com/searchsite/2018?search=HCI1469BU. To sign up to the vSAN Beta which is covering some of the Data Protection, Cloud Native Storage, and File Services visit http://www.vmware.com/go/vsan-beta