SAP HANA High Availability Cross-Zone Solution on Alibaba Cloud #

The next sections contain information about how to prepare the infrastructure.

2.2 Creating VPC #

 

First, create a VPC via Console→Virtual Private Cloud→VPCs→Create VPC. In this example, a VPC named suse_hana_ha in the Region EU Central 1 (Frankfurt) has been created:

There should be at least two VSwitches (subnets) defined within the VPC network. Each VSwitch should be bound to a different Zone. In this example, the following two VSwitches (subnets) are defined:

• Switch1 192.168.0.0/24 Zone A, for SAP HANA Primary Node;

• Switch2 192.168.1.0/24 Zone B, for SAP HANA Secondary Node;

2.3 Creating ECS Instances #

 

Two ECS instances are created in different Zones of the same VPC via Console→Elastic Compute Service ECS→Instances→Create Instance. Choose the "SUSE Linux Enterprise Server for SAP Applications" image from the Image Market place.

In this example, two ECS instances (hostname: hana0 and hana1) are created in the Region EU Central 1, Zone A and Zone B, within the VPC: suse_hana_ha, with SUSE Linux Enterprise Server for SAP Applications 12 SP2 image from the Image Market Place. Host hana0 is the primary SAP HANA database node, and hana1 is the secondary SAP HANA database node.

2.4 Creating ENIs and Binding to ECS Instances #

 

Create two ENIs via Console→ Elastic Compute Service ECS→Network and Security→ENI, and attach one for each ECS instance, for HANA System Replication purposes. Configure the IP addresses of the ENIs to the subnet for HANA System Replication only.

In this example, the ENIs are attached to the ECS instances hana0 and hana1. In addition, the IP addresses are configured as 192.168.0.83 and 192.168.1.246 within the same VSwitches of hana0 and hana1, and put into the VPC: suse_hana_ha

Meanwhile, within the Guest OS, /etc/hosts should also be configured.

According to the example at hand, run the following two commands on both sites:

echo "192.168.0.82 hana0 hana0" >> /etc/hosts

echo "192.168.1.245 hana1 hana1" >> /etc/hosts

The output looks as follows:

2.5 Creating NAT Gateway and configure SNAT entry #

 

Now create an NAT Gateway attached to the given VPC. In the example at hand, an NAT Gateway named suse_hana_ha_GW has been created:

After having creating the NAT Gateway, you need to create a corresponding SNAT entry to allow ECS instances within the VPC to access public addresses on the Internet.

Note

An Alibaba Cloud specific STONITH device and Virtual IP Resource Agent are mandatory for the cluster. They need to access Alibaba Cloud OpenAPI through a public domain.

In the example at hand, two SNAT entries have been created, for ECS instances located in a different network range:

2.6 Creating STONITH Device and Virtual IP Resource Agent #

 

Download the STONITH fencing software with the following command:

wget http://sap-automation-cn-beijing.oss-cn-beijing.aliyuncs.com/software/aliyun-pacemaker_new.zip

For an HA solution, a fencing device is an essential requirement. Alibaba Cloud provides its own STONITH device, which allows the servers in the HA cluster to shut down the node that is not responsive. The STONITH device leverages Alibaba Cloud OpenAPI underneath the ECS instance, which is similar to a physical reset / shutdown in an on-premise environment.

Extract the package and install the software.

tar –xvf aliyun-ecs-pacemaker.tar.gz
./install

Install Alibaba Cloud OpenAPI SDK.

pip install aliyun-python-sdk-ecs aliyun-python-sdk-vpc aliyuncli

Configure Alibaba Cloud OpenAPI SDK and Client.

aliyuncli configure

Get your Access Key as shown below:

The next sections contain information about the required software.

zypper in -t pattern ha_sles

zypper in SAPHanaSR SAPHanaSR-doc

3.3 SAP HANA Installation #

 

Next, install the SAP HANA software on both ECS instances. Make sure the SAP HANA SID and Instance Number are the same (this is required by SAP HANA System Replication). It is recommended to use hdblcm to do the installation. For details refer to the SAP HANA Server Installation and Update Guide at https://help.sap.com/viewer/2c1988d620e04368aa4103bf26f17727/2.0.03/en-US.

In the example at hand, both node are installed with SAP HANA (Rev. 2.00.030.00), and SID: JL0, Instance Number: 00.

3.4 SAP Host Agent Installation #

 

When you have finished the HANA installation with hdblcm as mentioned above, the SAP Host Agent should already be installed on your server. To install it manually, refer to the article Installing SAP Host Agent Manually: https://help.sap.com/saphelp_nw73ehp1/helpdata/en/8b/92b1cf6d5f4a7eac40700295ea687f/content.htm?no_cache=true.

Check the SAP Host Agent status after you have installed SAP HANA with hdblcm on hana0 and hana1:

The following sections detail how to configure SAP HANA System Replication.

4.1 Backing up SAP HANA on Primary ECS Instance #

 

To do a backup on SAP HANA, you can either use SAP HANA studio or hdbsql as the client command tool.

The backup command is

• For HANA 1 single container mode:

BACKUP DATA USING FILE('COMPLETE_DATA_BACKUP');

• For HANA 2 with multitenant as default mode (You should back up systemDB and all tenantDB as shown below in the example):

BACKUP DATA for <DATABASE> using FILE('COMPLETE_DATA_BACKUP')

Command line example:

BACKUP DATA for SYSTEMDB using FILE('COMPLETE_DATA_BACKUP')

BACKUP DATA for JL0 using FILE('COMPLETE_DATA_BACKUP')

In this example for HDB Studio, the SAP HANA database backup is executed on both ECS instances as shown below:

vi /hana/shared/<SID>/global/hdb/custom/config/global.ini

[system_replication_hostname_resolution]
<IP> = <HOSTNAME>

[system_replication_hostname_resolution]

192.168.1.246 = hana1

[system_replication_hostname_resolution]

192.168.0.83 = hana0

4.4 Enable SAP HANA System Replication on Primary Node #

 

Log on to the primary node with: su - <sid>adm;

Start HANA with: HDB start;

Enable System Replication with:

hdbnsutil -sr_enable --name= [primary location name]

[primary location name] should be replaced by the location of your primary SAP HANA node.

For the example at hand, the following command is used:

hdbnsutil -sr_enable --name=hana0

Note

All of the above operations are done on the Primary node.

4.5 Register the Secondary Node to the Primary SAP HANA Node #

 

Log on to the secondary node with: su - <sid>adm;

Stop SAP HANA with: HDB stop;

Register the Secondary SAP HANA node to the Primary SAP HANA node by running the following command:

hdbnsutil -sr_register --remoteHost=[location of primary Node] --remoteInstance=[instance number of primary node] --replicationMode=sync --name=[location of the secondary node] --operationMode=logreplay

For the example at hand, the following command is used:

hdbnsutil -sr_register --name=hana1 --remoteHost=hana0 --remoteInstance=00 --replicationMode=sync --operationMode=logreplay

Start SAP HANA with: HDB start;

Verify the System Replication Status with the following command:

hdbnsutil -sr_state

In the example at hand, the following status is displayed on the secondary SAP HANA node hana1:

Note

All of the above operations are done on the Secondary node.

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