More memory for SAP HANA on SLES 11 for POWER

Many companies are now running their businesses with SAP HANA on IBM POWER servers. SUSE has seen huge customer demand for SUSE Linux Enterprise Server for SAP Applications 11 SP4 since it became available in August 2015.

SAP HANA is an ideal workload for IBM POWER server due to the performance, reliability and scalability features provided by Power Systems servers. SAP HANA customers were able to boost their performance, save time on deployments and protect critical business operations with built-in business continuity capabilities by using POWER system with SLES for SAP Applications 11 SP4.

As customers scaled up their SAP HANA environments, they found that they needed support for very large physical memory configurations in an LPAR (VM), beyond the 1.5TB supported by SLES 11.

Technically, this was a challenging problem. Expanding memory beyond 1.5TB would require changing the SLES 11 kernel page table structure impacting kernel ABIs. These changes could negatively affect compatibility for applications that use the kernel ABI. Retesting all existing applications would be impractical for a mature operating system like SLES 11 that first became available in 2009.

Fortunately, the product and engineering teams at SUSE were able to come up with an approach that preserved compatibility for existing SLES 11 customers while enabling very large memory support for SAP HANA on POWER. The solution was the introduction of an additional, “Bigmem” kernel.

The Bigmem kernel (kernel-bigmem) is an additional Linux kernel available for SLES for SAP Applications 11 SP4 customers through the maintenance channel. The Bigmem kernel is modified to provide support for up to 32TB on IBM POWER.  Customers using SAP HANA can optionally use the BIgmem kernel to support any size memory up to 32TB. Customers who are using SLES 11 for workloads other than SAP HANA will continue to use the standard kernel. Moving forward, both kernels will be supported by SUSE on SLES for SAP Applications 11 SP4.

The Bigmem kernel also increases the number of threads supported by SLES for SAP Applications 11. This is required for systems that have more than 1024 logical CPUs such as an IBM Power System E880 configured with 192 physical CPU core with SMT8, resulting in 1536 logical CPU threads.

IBM, SAP and SUSE have rigorously tested the Bigmem kernel with SAP HANA for several months and the official certification is available. The recommended patch list can be found at https://download.suse.com/Download?buildid=abdTREGeaIw~

Note that the Bigmem kernel is not supported for applications other than SAP HANA.

Also, note that clients implementing SAP HANA on SLES for SAP Applications 12 do not need the Bigmem kernel because the base kernel in SLES 12 already supports up to 32 TB of memory.

Source: Suse.com, by Jay Kruemcke SUSE product manager for SUSE Linux Enterprise Server for ARM and Power platforms and for High Performance Computing at SUSE.