Following Architectural Decisions (ADs) were made as part of this Reference Architecture. Different ADs might lead to different Reference Architectures.
| ID | AD1 |
|---|---|
| Name | High Availability Concept |
| Description | SAP HANA is supporting multiple fundamentally different High Availability concepts. One needs to be selected. |
| Assumptions | Overall design should support both single-node and scale-out in parallel next to each other. Objective is to minimize the Recovery Time Objective (RTO). |
| Options | 1. SAP HANA Host Auto-Failover (HAF) 2. SAP HANA System Replication (synchronous) |
| Decision | 2. SAP HANA System Replication (synchronous) |
| Justification | - this is the only option that is supporting REQ2 for scale-out systems - the Recovery Time Objective (RTO) values are significantly smaller compared to 1. - this option is supporting additional features like Active/Active (Read Enabled) or Secondary Time Travel |
| Comment | Recommended Replication Mode is SYNC in case there is possible shared Single Point of Failure (SPOF) or SYNCMEM in case of two physically separated infrastructures.Recommended Operation Mode is logreplay (or logreplay_readaccess). |
| ID | AD2 |
|---|---|
| Name | Disaster Recovery Concept |
| Description | SAP HANA is supporting multiple fundamentally different Disaster Recovery concepts. One needs to be selected. |
| Assumptions | - |
| Options | 1. Storage Replication 2. SAP HANA System Replication (asynchronous) |
| Decision | 2. SAP HANA System Replication (asynchronous) |
| Justification | - option 1. might or might not be available and is unlikely to work cross-platform - option 2. is part of the product and therefore always available, it is platform independent and will work even cross-platform - as part of option 2. all data pages are checked for consistency during the transfer to secondary site |
| Comment | Replication Mode must be ASYNC to avoid performance impact.Operation Mode must be same for all tiers (either delta_datashipping or logreplay/logreplay_readaccess), combining Operations Modes is not supported.Operation mode logreplay_readaccess is available only between primary and secondary system. |
Note: Combination of AD1 and AD2 will lead to usage of SAP HANA Multitarget System Replication (or SAP HANA Multitier System Replication in case of SAP HANA 1.0).
| ID | AD3 |
|---|---|
| Name | High Availability Takeover Automation |
| Description | There are different options/products how High Availability Takeover can be executed. One needs to be selected. |
| Assumptions | Objective is to minimize the Recovery Time Objective (RTO). |
| Options | 1. Manual Takeover (no automation) 2. Pacemaker Cluster (Linux native solution) 3. 3rd Party Clustering Solution |
| Decision | 2. Pacemaker Cluster (Linux native solution) |
| Justification | - option 1. is not satisfying requirement to minimize the Recovery Time Objective (RTO) value - option 2. is seen as recommended option by both OS vendor and SAP and is most common HA solution - option 3. might not be available across all platforms |
| Comment | Take into account specific Implementation Guidelines for each Infrastructure Platform. |