Sizing Recommendations
Overview
In a highly-available configuration, when DataCore virtual disks (vDisks) are mirrored between a pair of DataCore Servers, I/O load will be shared between the pair. This means that when one of the DataCore Servers is unavailable – for any reason – the remaining DataCore Server must be able to manage the entire load from all active HANA Nodes.
The minimum configuration for a pair of DataCore Servers, with 8 Gbit/s Fibre Channel (FC) connections, is up to 4 ‘active’ HANA nodes with any number of ‘standby’ nodes. The same configuration using 16 or 32 Gbit/s FC connections can manage up to 8 active HANA nodes with any number of standby nodes.
There is no limit to the amount of HANA nodes that can be served virtual disks by SANsymphony, but only a maximum of 768 HANA nodes can be ‘active’ at any time.
HANA nodes that are not ‘active’ (i.e., they are in a ‘standby’ role) technically will still have access to any virtual disk served to it but will only be considered as ‘active’ if another active node fails and the HANA application changes the role of the standby node to an active one.
Fibre Channel Ports
The number of FC ports in the DataCore Server will affect the sizing calculation. A DataCore Server must have at least one of each of the following dedicated port roles.
- Front-end (FE) – the port the HANA nodes connect to as a SCSI Target Mode connection.
- Back-end (BE) – the port the HANA certified storage connects to as a SCSI Initiator.
- Mode connection.
- Mirror (MR) - the port(s) each pair of DataCore Servers connects to between themselves for mirroring the HANA data as both SCSI Initiator and Target connections.
- No port can be assigned to more than one role.
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The number of each type of port must be the same for all roles – e.g., 2 FE + 2 BE + 2 MR Ports. Where there are odd numbers of ports use the smallest number possible – e.g., with 7 fibre channel ports use 2 FE + 2 BE + 2 MR port with 1 port unused.
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SANsymphony System Managed Mirroring (SMM) is recommended to achieve full load distribution across all MR Ports when there are more than 2 MR Ports existing per DataCore Server.
CPU Cores and Sockets
There needs to be enough CPU sockets to support the PCIe bus lanes of all fibre channel adaptors in the DataCore server. A minimum of two sockets are suggested.
While dual-ported adaptors will reduce the number of PCIe buses needed, DataCore do not recommend using quad-port adaptors as the PCIe slot bandwidth requirements for these devices are usually oversubscribed which will affect performance.
Each FC port should, ideally, have a CPU core available for it to scale the I/O in parallel. Hyper-threaded, virtual cores are recommended only if they are Intel Skylake or AMD Epyc CPU’s (or later).
With two socket systems, this will allow a scaling-up of the DataCore Servers to six FE ports, each using 16 Gbit/s connections, allowing up to 24 active SAP HANA nodes per pair of highly available DataCore Servers.
Memory Cache
Allow at least 200 MB of system RAM for each vDisk presented to a HANA node.
Key Performance Indicator Requirements
The following Key Performance Indicators (KPI) need to be met:
SAP Note 2493172
HANA HW CLOUD OPTIMIZATION TOOLS 2.0