vSAN Licensing: Expanding Clusters and Setting off Alerts

vSAN licenses are assigned per-cluster, so whilst the total number of vSAN licenses in a vCenter inventory might match the total number of vSAN host CPUs, they may not be assigned correctly to the clusters. This will trigger the critical vCenter alarm “License inventory monitoring”. This will also occur if a cluster is expanded (e.g. additional hosts and vSAN licenses are purchased) as it’s only possible to assign one license key to each cluster.

In the example screenshot here we have 2 vSAN license keys, each valid for 8 CPU. The total 16 CPU capacity matches the 16 CPU in use. However, one cluster has 10 CPUs (i.e. 5 dual socket hosts) and the other only 6 CPU. Therefore one license key is 2 CPU oversubscribed whilst the other has 2 free.

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The method to resolve this is to use the MyVMware license portal to split and merge your pool of vSAN licenses until you have license keys where the capacities match your cluster sizes, and then re-license the vSAN environment. This VMware KB article explains in detail how to do this divide, and merging is a similar process on the same interface: https://kb.vmware.com/s/article/2006972

In the example screenshot above, this was a case of splitting one of the 8 CPUs into a 6 and a 2, and then merging that 2 with the remaining 8 CPU key to create a 10 CPU key and a 6 CPU key which matched the cluster sizes. The old 8-CPU key that was split was removed from the license inventory.

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Content Library fails to create when target datastore contains a space

Symptoms

A quick note on an issue I spotted in VMware vSphere 6.5 when creating a new content Library. If the datastore being used for the new library contains a space in it’s name then the Create Content Library process fails. The error given is “The specified parameter was not correct: The provided storage backing xxxxx xx for library xxxxx-xxxx-xxxx-xxx is invalid.”. For example, if a second vSAN cluster has been created and the default name “vsanDatastore (1)” was used for the datastore.

 

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Solution

Rename the target datastore to a name which does not contain a space then repeat the Content Library creation process.

 

Notes

This occurred in my environment running vSphere 6.5 (vCenter VCSA build 6.5.0.14000) and hasn’t been thoroughly tested for repeatability (at least by me).

VMworld

VMworld 2018 Call for Papers

The Call for Papers for VMworld 2018 is now live, running until March 13th. As with last year, this is for both the US and Europe legs of the event, even though the Barcelona date has been moved to early November. This seems a little odd given the speed of change in tech, submitting a topic eight months before the event, but I’d hope that space is left in the program for new developments and releases to be covered when the show comes across the Atlantic.

If you’re interested in submitting a session, Eric Siebert has some good tips over on vsphere-land.com on how to get it approved. Having never submitted for the conference (with the exception of a vBrownbag appearance), I’m not going to offer any further advice from that point of view, but I do have one request as a regular attendee:

Appropriate Naming

Please, please, title and describe your session appropriately. Whilst phrases like “Deep Dive” or “Customer Story” often draw in the audience, they are going to leave disappointed if they get an introductory level view of the product, or the only reference to the customer is “we sold it to them”. A big crowd leaving bad feedback isn’t going to impress.

At last year’s event I saw some excellent Deep Dives – the vSAN Troubleshooting DeepDive (STO1315BE) and the vSphere 6.5 Host Resources Deep Dive (SER1872BE) are great examples of talks with some awesome in-depth content. However I was in another “Deep Dive” where the presenters spent a sizeable amount of time giving an introduction to the product in question before trundling through marketing slides. I’m not going to name and shame here- I raised it appropriately in the session feedback at the time- but it did feel like I’d wasted an hour out of my schedule. Time at the event is valuable and limited, so attendees try and get the most out of every hour.

Don’t let this detract anyone from attending and registering for sessions- in my experience the majority of sessions are well labelled in the Content Catalog- but if you are thinking of presenting please make sure to describe your session correctly and help improve the experience even more. I’m looking forward to seeing what sessions are going to be on the list this year, and hoping to be there in person (subject to obtaining a conference pass).

vSAN Editions

There are three major editions* of vSAN 6.6 available – “Standard”, “Advanced”, and “Enterprise”- so other than price what’s the difference between the three?

*aside from the “vSAN for Desktop” and “vSAN for ROBO” lines which address specific use cases- look out for later posts focusing on these.

Standard

Standard is the base offering and, like it’s more expensive cousins, is licensed per socket the same way that vSphere is- so a dual-socket host needs two licenses for vSphere and two licenses for vSAN. This edition gives you all the core features of the VMware software-defined storage platform; distributing VM storage across the converged hosts, supporting iSCSI access for non-virtualised workloads, and using Storage Policy-Based management to name a few.

Advanced

http://www.yellow-bricks.com/stickersshirts/Advanced, the next edition up the scale, gives benefits to vSAN platforms built on All-Flash. A vSAN host can be configured as “Hybrid” or “All-Flash”, hybrid uses spinning disks- HDD – for the capacity tier and flash disks for the cache tier. If your hardware uses the Hybrid model then there’s no advantage to using the Advanced edition as the additional features are only applicable to All-Flash configurations.

However, the Advanced edition provides major features which may tip the balance in the favour of the all-flash design when choosing a hardware platform, namely Erasure Coding, Deduplication, and Compression.

Deduplication (storing matching blocks of data only once), compression (using an algorithm to compress data), and erasure coding (basically arranging the data in a similar way to a RAID5/6 model but across hosts) are all features which can be used to reduce the amount of physical disk consumed by the data. Less space consumed = lower disk requirements = lower costs.  More detailed information on vSAN Space Efficiency can be found in the VMware docs.

As these three technologies can squash more data into your disk, they can provide more capacity for your spend and potentially offset the higher cost of SSD per gigabyte over HDD and the higher vSAN licensing price (Advanced is retailing at $1500 per socket more than Standard at time of writing). In the right circumstances it’s possible to design a higher capacity, better performing platform using the Advanced Edition+All-Flash route for the same cost of the Standard Edition+Hybrid design.

As with any data reduction technology, results can vary depending on workload. The VMware product page quotes savings of “up to” 7x from the deduplication and compression- in reality I’m seeing 2.5x in my own mixed server environment, but I’d expect VDI deployments to see higher figures. In my opinion All-Flash is the way forward and once you’ve made that decision then vSAN Advanced Edition wins over Standard in pretty much every situation.

Enterprise

The Enterprise edition takes the price up higher another $1500 per socket  (list price) at time of writing but adds Stretched Cluster with Local Failure Protection and Data-at-Rest Encryption.

The Encryption feature applies to whole vSAN cluster so everything stored on that datastore will be encrypted at rest. This allows dedupe and compression still to work, features that don’t provide any capacity benefits when using the alternative vSphere encryption. vSAN Encryption is configured using the same KMS service as vSphere- so a third-party Key Management Service is required, and you will want a non-encrypted (or alternatively encrypted) datastore/ cluster to host that on. As the encryption is a software offering expensive self-encrypting drives are not required.

The Stretched Cluster functionality allows a vSAN cluster to be designed to span across multiple datacentres and tolerate failure of an entire site. By using a witness host the cluster can detect the loss of a datacentre (or connectivity to it) and ensure that the storage is available using the alternative site. VMware High Availability ensures that any VMs which were running in the failed datacentre are powered on on the surviving site.

Summary

TL;DR.

There are three editions of regular vSAN- Standard, Advanced, and Enterprise. If you want to use a Stretched vSAN Cluster or vSAN Encryption then you need the Enterprise edition. If you don’t expect to use either of these (perhaps vSphere Encryption covers any encryption requirements) and have an all-flash hardware configuration then it makes sense to go with Advanced Edition. And finally, if you have a Hybrid hardware config then go with Standard Edition (or upgrade your spinning disks to flash).

Further Reading:

vSAN Introduction

What is vSAN?

This is a first post in a series on vSAN, VMware’s software-defined-storage offering. vSAN uses disks within the ESXi hosts to create a resilient scalable shared storage platform for the virtual infrastructure providing many of the features of SAN/NAS shared storage without the need for additional hardware. There are also operational, performance, and scaling benefits associated with integrating the storage into the hypervisor’s control.

Unlike some other software-defined-storage solutions, vSAN is not a separate appliance but instead is baked into the ESXi hypervisor. In fact there is no separate install; installation (which I’ll cover in a future post) is simply a case of applying a license and configuring the cluster through vCenter.

vSAN dates back to 2013, with a General-Availability launch in March 2014 (the first was version 5.5 which was part of ESXi 5.5U1) and has evolved to the current version- v6.6 at the point this post was written.

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