NAME¶

SAP HANA System Replication scale-out basic cluster configuration.

DESCRIPTION¶

The SAP HANA System Replication scale-out scenario needs a certain basic cluster configuration.

* CRM Basics

no-quorum-policy = freeze

The crm basic parameter no-quorum-policy defines how the cluster should act in case of quorum loss. With more than two nodes, the cluster must not ignore the quorum loss. For SAPHanaSR-ScaleOut, an odd number of nodes is required. Setting no-quorum-policy to 'freeze' won't allow the partition to shoot any other node when it doesn't have quorum. Cluster will not be able to add and start new resources.

default-resource-stickiness = 1000

The crm basic parameter default-resource-stickiness defines the 'stickiness' score a resource gets on the node where it is currently running. This prevents the cluster from moving resources around whithout an urgent need during a cluster transition.

concurrent-fencing = true

The crm basic parameter concurrent-fencing allows the cluster to fence more than one node at a time. This helps to reduce the time needed for a take over in case a whole data center is lost. If nodes are fenced one by one, the time needed would be equal to the number of nodes * stonith timeout. With concurrent-fencing enabled the time needed is always stonith timeout, independent of the number of nodes. See also pcmk_action_limit below.

migration-threshold = 50

The crm basic parameter migration-threshold defines how many errors on a resource can be detected before this resource will be migrated to another node.

record-pending = false

The op_default record-pending defines, whether the intention of an action upon the resource is recorded in the Cluster Information Base (CIB). Setting this parameter to 'true' allows the user to see pending actions like 'starting' and 'stopping' in crm_mon and Hawk.

* SBD STONITH Basics

pcmk_action_limit = -1

The sbd stonith parameter pcmk_action_limit defines the maximum number of concurrent fencing actions. It allows parallel fencing of multiple nodes. A value of '-1' means virtually unlimited. See also concurrent-fencing above.

pcmk_delay_max = 30s

The sbd stonith parameter pcmk_delay_max defines an upper limit for waiting before a fencing/stonith request will be triggerd. This parameter should prevent the cluster from unwanted double fencing in case of spilt-brain. It is required in two-node clusters. It might not be needed in usual SAPHanaSR-ScaleOut setups.

EXAMPLES¶

* crm basic configuration

Below is an example crm basic configuration for SAPHanaSR-ScaleOut. Shown are specific parameters which are needed. Some general parameters are left out. The example has been taken from SLE-HA 11 SP4. It should work on SLE-HA 12 SP1 and later as well.

* crm sbd stonith configuration

To complete the SBD setup, it is necessary to activate SBD as STONITH/fencing mechanism in the CIB. The SBD is normally used for SAPHanaSR-ScaleOut instead of any other fencing/stonith mechanism.

BUGS¶

In case of any problem, please use your favourite SAP support process to open a request for the component BC-OP-LNX-SUSE. Please report any other feedback and suggestions to feedback@suse.com.

SEE ALSO¶

ocf_suse_SAPHanaTopology(7) , ocf_suse_SAPHanaController(7) , sbd(8) , stonith_sbd(7) , crm_no_quorum_policy(7) , crm(8) , crm_simulate(8) , SAPHanaSR-ScaleOut(7) ,
https://www.suse.com/products/sles-for-sap/resource-library/sap-best-practices.html ,
https://www.clusterlabs.org

AUTHORS¶

F.Herschel, L.Pinne.

COPYRIGHT¶

(c) 2018 SUSE Linux GmbH, Germany.
For details see the GNU General Public License at http://www.gnu.org/licenses/gpl.html