Deployment points for Virtual Persistent Memory

SAP and Intel cite two aspects here. Firstly, faster start times for the Hana database and secondly, the use of cheaper storage media compared to traditional memory.

First, let's take a more differentiated look at the definition of the start time of a Hana database: The start time of Hana plays a role with regard to two aspects. The first part is the start of the processes and a small set of structures, after which an SAP user can already log into the database.

The second part is loading the data into the so-called Hana Main Area, which accounts for around 90 percent of the total start-up time. It should be noted that Hana loads the data intelligently, so that the first SAP users can work on the database without the data being loaded completely and with reduced performance.

This means that the solution for persistent storage media provided by SAP addresses 90 percent of the start-up time until optimum performance is achieved.

When choosing storage media, it is important to ensure that they are not only inexpensive, but also redundant and fast. If one of the persistent storage media fails and has no redundancy or hot-plug functionality, this means a failure for the entire business application and the restart is then carried out from external storage media, i.e. slowly, in order to reinitialize the persistent storage media.

In addition, performance is another criterion that should be taken into account, as the persistent storage media replace part of the main memory.

Fast start

Customer surveys have shown that persistent storage media alone cannot be the answer to fast Hana startup times, as there are other criteria to consider, such as virtualizability and flexibility of the solution; easy sharing of existing hardware and mobility are leading aspects; and a tailored solution without loss of performance.

Depending on the size of the database, the start time also varies and therefore also the choice of suitable technology to reduce the start time.

Robustness of the solution

The persistent storage media must be implemented with high availability in order to avoid new risks that cause downtime. IBM has therefore put together a flexible portfolio, which is explained in more detail below.

All solutions are based on the same storage media. This means that customers continue to have maximum performance, the familiar robustness, do not require any special hardware and can still save on physical storage in combination with other technologies and best practices.

SAP Hana on Power was announced in 2015. Based on the SAP TDI approach (Tailored Datacenter Integration), IBM solutions have been available since 2016 to optimize the startup times of a Hana database.

It is important to note that the solutions are all complementary, i.e. the start time optimization is further improved by combining them. Technical documentation on these options can be found on IBM Techdocs: SAP Hana on IBM Power Systems and IBM System Storage - Guides.

Native Storage Extension

The first step in all cases should be to reduce the amount of data to be loaded. Native Storage Extension (NSE) is a power-verified solution that either reduces the main memory or increases the amount of data with the same memory and core requirements.

It is important to consider the combination here. Faster storage subsystems optimize the use of the buffer through fast reloading and - if no persistent storage is available - also the Hana start time.

The use of NSE does not entail any restrictions in terms of flexibility, robustness and mobility. If the sizing for NSE is adhered to and no frequently required data is reloaded, the maximum reduction in performance is less than five percent.

Storage subsystems

Some IBM storage systems are now equipped with NVMe and in some cases with additional NVM technology (e.g. Optane). In the data area, the improved read speed is particularly important.

This means that faster storage systems can both improve the start-up time for the initial loading of all persistent storage solutions (including Intel) and make the use of NSE more intensive.

IBM's NVMe is also better at writing small blocks, which leads to improved Hana response time for database logging, write-intensive operations and especially when loading new data or OLTP loads.

By using IBM's NVMe/NVM-based storage systems, there are no restrictions in terms of flexibility, robustness and mobility. In addition to the improved start time, the response time and use of NSE are also optimized.

Internal PCI NVMe cards

IBM Power Servers have the option of accommodating four NVMe cards per slot. Due to the short connections, the read and write speed is better than with external storage solutions. The improvement in boot time is around twice as high as with fast external storage.

The NVMe configuration and the number of cards differentiate between a purely internal version and the "Rapid Cold Start" solution. With a pure NVMe configuration, such as with the H922 and H924 servers, the failure of a card is protected by a raid and therefore twice the amount of space is required. With the "Rapid Cold Start" solution, the NVMe cards only serve as a read cache and the data is protected on the SAN.

With both architectures, LPAR mobility (LPM and SRR) is not possible due to the use of dedicated hardware or is only possible via manual intervention. In combination with SAP Hana System Replication (HSR), for example, the deficit can already be easily compensated for today.

IBM's persistent storage solutions

Both solutions, Temp-FS and Virtual Persistent Memory, are based on the main memory and therefore require no special hardware and have no performance disadvantages.

Both can be used by simply configuring the logical partition. The larger the Hana database, the more valuable the multiple acceleration of the start time. For very large databases, the factor can be over 17 times higher.

The main difference comes down to two points: Mobility is only possible today with the Temp-FS solution, but Temp-FS only accelerates the Hana restart. Virtual Persistent Memory, on the other hand, cannot support mobility via Life Partition Mobility (LPM) or Simplified Remote Restart (SRR) today, but this solution improves the restart of the complete logical partition.

All listed hardware components that are used for the quick start of Hana have been listed among the top solutions in the ITIC report for years. In addition to the high reliability of the hardware, the IBM Power Platform offers extended options.

Logical partitions can be moved transparently between servers via Life Partition Mobility. The mobility of shutdown systems and partitions is possible via Simplified Remote Restart.

In addition, PowerVM Remote Restart offers disaster and high availability solutions that can orchestrate the start-up of entire SAP landscapes in a new data center at the touch of a button using enterprise server pools - i.e. the core licenses are automatically transferred to the new server - and dynamic resource management. The well thought-out portfolio optimizes availability and at the same time reduces the costs for acquisitions, operation and licenses.