At Microsoft Ignite this week, the Power BI team unveiled the next generation of the architecture for their “dedicated capacity” customers. This architecture promises to resolve many of the issues experienced with the first generation of Premium, and opens up several possibilities moving forward.
Gen-1
The Power BI dedicated capacity SKUs (which include Premium) were introduced 3 years ago in order to provide a scalable pricing model, and to provide predictable performance. Unlike the Pro SKU, which is licensed per user, these SKUs represent specific sets of resources running in Azure. There are currently 3 SKUs in this category, the A SKU (purchased hourly from Azure, the EM SKU (for embedding), and the well know P or Premium SKU.
When an organization purchases one of these SKUs, they are essentially purchasing memory, CPU cores and storage. The isolation allows for predictability, but it also means that when the resources become over allocated, catastrophic errors can occur. Refreshing a data set can also be particularly memory intensive, and the memory usage during a refresh could increase by more than double what might be normally required. This has an impact on normal operations during refresh, and means that capacity need to be over-sized to accommodate refresh in some cases.
Once acquired, Gen-1 capacities need to be configured, and decisions made as to what services to allow, and how many resources to allocate to them. It’s not always obvious as to what those settings should be. I’ve also seen situations where an overzealous administrator gets so excited about the new Premium capacity that they assign hundreds of workspaces to it, and bring reports to their knees.
Gen-2 – A Different Approach
The new “Gen-2” architecture aims to deliver the isolation and predictability that dedicated capacity brings, without the drawbacks. Gen-2 is in fact, not dedicated, as resources are drawn from a massive pool as needed. However, the performance level is guaranteed, and is focused on CPU cycles. In fact, memory is not even a consideration, apart from per-dataset overall size limits.
Memory will be allocated as needed to refreshes, ending the need to worry about refreshes failing, or impacting end user experiences. The CPU charge for refreshes will be allocated immediately, but the usage allocation will be spread out throughout the day. This provides consistent fast performance without requiring resource overallocation to handle peaks due to resourcing. Memory is no longer a factor whatsoever for refresh.
This architecture also allows for automatic scale up/down for intensive or unpredictable workloads. Administrators will no longer need to make so many decisions up front, or react to changes as frequently. If autoscale is not enabled, queries can potentially be slowed down, but a refresh kicking off can no longer make reports unavailable. The new architecture is moving back to a SaaS model, after being rather close to IaaS with Gen 1
In the past, services that required full isolation like Paginated reports were not available on some of the lower end A and EM SKUs. With this new architecture, they will be available on all of them. In fact, with the newly announced Premium per user SKU, they will even be available on a per user basis.
This new architecture will be available to all of the “dedicated” SKUs, A, EM and P. The preview of the new P SKU will begin later in 2020. As an ISV, I am particularly interested in this new architecture for the A SKUs. The memory spikes caused by large refreshes have been particularly problematic for us in the past. Gen-2 architecture appears to be just what the doctor ordered.
I have often referred to this group of SKUs as the dedicated capacity SKUs in the past, but with this change, that term is no longer accurate. With the term Premium being so pervasive, I think we’ll just have to call them all Premium SKUs, whether they are P or otherwise.
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