Metro Cluster High Availability or SRM Disaster Recovery?

Several years I continuously try to explain my customers that metro cluster is not disaster recovery. I have finally found some time and summarize my thoughts into slide deck which I published on SlideShare. I'm planning to present it at Czech VMUG local meeting on 6 December this year. More info about this particular Czech VMUG event is here.

The goal of my presentation is to explain the difference between multi site high availability (aka metro cluster) and disaster recovery. General concepts are same for any products but presentation is obviously more tailored for specific VMware products and technologies.

You can look at presentation here on SlideShare ...

Metro Cluster High Availability or SRM Disaster Recovery? from David Pasek

It would be great to see you at the event if you will be in the town. But in the meantime don't hesitate to write any comment or feedback here and we can have good discussion as there are still two months till the event.

BTW: Kudos to Stanislav Jurena @stan_jurena who already did several reviews and gave me some comments and feedback before first public release.  

General recommendations for stretched vSphere HA Cluster aka Metro Cluster Storage (vMSC)

This is just a brief blog post with general recommendations for VMware vSphere Metro Cluster Storage (aka vMSC). For more holistic view, please read white paper "VMware vSphere Metro Storage Cluster Recommended Practices"

vSphere HA Cluster Recommended Configuration Settings:

• Set Admission Control - Failover capacity by defining percentage of the cluster (50% for CPU and Memory)
• Set Host Isolation Response - Power Off and Restart VMs
• Specify multiple host isolation addresses - Advanced configuration option das.isolationaddressX
• Disable default gateway as host isolation address - Advanced configuration option das.useDefaultIsolationAddress=false
• Change the default settings of vSphere HA and configure it to Respect VM to Host affinity rules during failover - Advanced configuration option das.respectVmHostSoftAffinityRules=true
• The minimum number of heartbeat datastores is two and the maximum is five. VMware recommends increasing the number of heartbeat datastores from two to four in a stretched cluster environment Advanced configuration option das.heartbeatDsPerHost=4
• VMware recommends using "Select any of the cluster datastores taking into account my preferences" for heartbeat datastores and choose two datastores (active distributed volumes/LUNs) on each site. 
• PDL and APD considerations depends on stretched cluster mode (uniform/non-uniform). However, VMware recommends to configure PDL/APD responses therefore VM Component Protection (VMCP) must be enabled and response should be set to "Power Off and Restart VMs - Conservative". Detail configuration should be discussed with particular storage vendor. 

vSphere DRS Recommended Configuration Settings:

• DRS mode - Fully automated
• Use DRS VM/Host rules to set VM per site locality
• Use DRS "Should Rules" and avoid the use of "Must Rules"

SIOC/SDRS

• Based on KB 2042596 SIOC is not supported
• Based on KB 2042596 SDRS is only supported when the IO Metric function is disabled.

Distributed (stretched) Storage Recommendations:

• Always consult your configuration with your storage vendor
• VMware highly recommends to use storage witness (aka arbitrator, tie-braker, etc.) in third site.

Custom automation for compliance check and / or operational procedures Recommendations:

• VMware recommends manually defining “sites” by creating a group of hosts that belong to a site and then adding VMs to these sites based on the affinity of the datastore on which they are provisioned. 
• VMware recommends automating the process of defining site affinity by using tools such as VMware vCenter OrchestratorTM or VMware vSphere PowerCLITM. 
• If automating the process is not an option, use of a generic naming convention is recommended to simplify the creation of these groups. 
• VMware recommends that these groups be validated on a regular basis to ensure that all VMs belong to the group with the correct site affinity.

Other relevant references:

1. VMware vSphere Metro Storage Cluster Recommended Practices
2. Setting Multiple Isolation Response Addresses for VMware High Availability (1002117)
3. vSphere HA respecting VM-Host should rules?
4. Using EMC VMAX Storage in VMware vSphere Environments

Compellent Storage Center Live Volume and vSphere Metro Cluster

Are you interested in metro clusters (aka stretched clusters)?

Watch this video which introduces the new Synchronous Live Volume features available in Dell Compellent Storage Center 6.5.

And if you need more technical deep dive use this guide focuses on two main data protection and mobility features available in Dell Compellent Storage Center: synchronous replication and Live Volume. In this paper, each feature is discussed and sample use cases are highlighted where these technologies fit independently or together.

Compellent Live Volume curretnly doesn't support automated fail-over based on arbiter on third site so that's the reason why it is not certified as VMware vSphere Metro Cluster storage. Certification is just a matter of time. However, you can leverago Compellent Live Volume with vSphere. The only drawback is that whole storage node fail-over has to be done manually which can be enough or preferred method in some environments.