====== SVC Enhanced Stretch Cluster configuration ======

===== SVC cabling and zoning =====

Example of cabling

In the best recommandations, alternate one port on Fabric SAN A (blue), then a port on B (red)...

{{:storage:svc_fc_connexions_08.png?4000}}

{{:storage:svc_fc_connexions_09.png?2000}}


Set the port mask to 11, so only ports 1 and 2 are able to communicate in node
<cli prompt='>'>
SVC:superuser>chsystem -localfcportmask 00001100 

SVC:superuser>lssystem |grep mask
local_fc_port_mask 00000000000000000000000000000000000000000000000000000000001100
</cli>

FIXME Why using 2 set of ports for host with different speed flagged 16Gb and 32Gb?\\
It's a best practice preventing SVC ports to negotiate between different speeds on hosts. Dedicated ports for high speed traffic. But on SAN switches leave the auto-negotiation so both can do 32Gb.

{{:storage:SAN zoning for SVC enhanced stretch cluster.png?650}}

SVC port connexion to SAN SW

https://www.ibm.com/support/pages/troubleshooting-svcstorwize-npiv-connectivity 

===== Storage connectivity =====

Nowadays (2024), <color #ed1c24>storage using NVMe are not supported</color>, only SCSI over FC. Hosts are supported with NVMe over FC, SCSI over FC, ... network storage protocols

For storage IBM change the layer at storage array to **storage**
<cli prompt='>'>
V7000:superuser> chsystem -layer storage
</cli>


  * Zone the FC SCSI NPIV (vWWPN) port from storage to SVC physical port (pWWPN)
  * For node inter-connection use also pWWPN only.
  * For hosts, use vWWPN with SCSI or NVMe protocols.

On SAN switch, for each storage ports, increase the **buffercredit to 40** for 16Gb or 32Gb
<cli prompt='>'>
sansw01:admin> portcfgfportbuffers --enable 0 40
</cli>

===== Configuring Enhanced Stretch Cluster =====

Before configuring all SVC nodes, wait:
  * Configure the first node as a cluster node
  * Start the other nodes
  * Do the private zoning
  * All other nodes started 'll be candidates (if they are still configured, go to the GUI and do a **remove node**)
  * Add the candidates nodes to the cluster
  * configure ALL service IP (on each node)
  * Download and install the IP quorum (check if it's active)
  * Create the zoning for the external storage (controllers)
  * Change the external storage **layer**

Now you are ready to configure the Enhanced Stretch Cluster

You can use either the GUI or the command line

3 sites are available by default (lssite), site 3 can't be set as it's assigned to IPquorum
  * chnode -site site_id node node_id
  * chcontroller –site site_id controller_id
  * chost -site site_id host_name
  * chsystem -topology stretched

Now you can check the result
<cli prompt='>'>
SVC:superuser> lssystem | grep topology
</cli>