Virtustream Blog

Intel® Optane™ for SAP HANA®: The Persistent Memory Payoff


in SAP, Cloud, Technology

I get it. Storage can be boring. You’ve been using DRAM and SSDs in your datacenters for years, maybe even a decade or longer, and everything has worked according to your mission-critical requirements. So why should you bother upgrading? Instead, you could spend money where it might be considered more innovative for your business, right? On CPUs, graphics chips or network modifications, for example.

But here’s the tough reality when you don’t pay enough attention to storage and memory: achieving maximum datacenter optimization is not possible if memory bandwidth or capacity are causing bottlenecks in the overall system performance. When using DRAM and volatile memory, especially for complex SAP HANA® systems and applications, there is a ceiling on performance. Although improvements in other areas of your environment might seem more enticing from a productivity and speed standpoint, keeping your storage up-to-date has become a fundamental requirement for mission-critical workloads.

Advancement in memory capabilities is critical to accommodate growing end-user requirements, which is why Virtustream is offering the option of Intel® Optane™ DC Persistent Memory, also known as PMEM, for our customers looking to directly address DRAM limitations head on.

Confronting DRAM Limitations

Intel Optane memory has two primary distinctions that make it extremely capable for addressing DRAM limitations.

  • Massive memory capacity: Intel Optane memory is available at 128GB, 256GB and 512GB, a range substantially greater than typical DRAM solutions, allowing for more data to pass through the memory bus lanes.
  • Persistent memory technology: Persistent memory allows assigned applications to retain data during power cycles.

A configuration guide from Intel, “Intel® Optane™ Persistent Memory and SAP HANA® Platform,” and a brief overview from Dell EMC, Advantages of PowerEdge Servers Configured with Intel® Optane™ DC Persistent Memory Module, do an excellent job covering the technical details of both of these points. In addition to the two distinctions above, Intel Optane DC Persistent Memory technology is offered in two operating modes, each with unique advantages designed to meet an enterprise’s specific use cases.

The overview from Dell EMC has this to say about both modes: 

  • Memory Mode: Strongly emphasizes building large storage capacity environments around the memory space. Memory Mode’s primary benefit is superior memory capacity, which can be used on memory bus lanes.
  • Application Direct Mode: Highlights the advantage of reduced latency that persistent memory can provide, with bandwidth speeds up to 2.7x faster than non-volatile memory express (NVMe). Using Application Direct Mode, in-memory data survives power cycles, allowing for minimal latency among large memory environments.
Volatile Memory vs. Persistent Memory: The Payoff

Traditionally, SAP HANA uses volatile memory and synchronizes it with the persistence level on disk using mechanisms such as save points. This can present a disadvantage for an enterprise running cloud-based workloads, given that during an SAP HANA restart all data must be reloaded from disk into memory. This process can result in an extended period of time until all data is back in memory.

Persistent memory provides the opportunity to combine fast access (like memory) with durable storage (like disk) that is maintained during restarts or crashes. Importantly for those running on SAP HANA, this can be used as the main storage for column store tables, typically the dominating factor impacting data space consumption in SAP HANA environments.

SAP HANA with Intel Optane

According to a blog earlier this year from SAP, most applications rely solely on the operating system for memory allocation and management, and SAP HANA is no exception. However, when comparing applications strictly from a memory perspective, SAP HANA has an inherently high degree of control over memory management allowing for maximum optimization.

SAP HANA extends seamlessly to persistent memory and can identify which data structures can benefit the most from implementing it. Additionally, SAP HANA automatically detects persistent memory hardware and adjusts itself by placing these data structures in persistent memory, while all others remain in DRAM. These capabilities are only available when running in Application Direct Mode, however, as Memory Mode (which is not used by SAP HANA) doesn’t offer the same level of data persistence, instead focusing on cheaper and/or larger main memory.

Persistent memory has been shown to deliver multiple benefits to end users in comparison to DRAM, such as ensuring business continuity by drastically reducing SAP HANA index server start times.

As shown in this graphic from Intel’s configuration guide (link above), Intel Optane DC persistent memory delivers faster SAP HANA database starts to help ensure business continuity and meet service-level agreements (SLAs).  Overall, persistent memory offers tremendous benefits to enterprises running SAP HANA, and can truly remove the ceiling on your application performance.

If you’re interested in learning more about how Virtustream Enterprise Cloud efficiently manages large SAP migration and implementations, read about our SAP solutions and xStreamCare Services today.

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