• This topic has 3 replies, 3 voices, and was last updated August 30, 2019 by Matthew W.

Does shared storage make 2 hosts "redundant"?

  • Hans K
    August 30, 2019 04:45:02 AM

    Hi,

    Question: We are running two sites: Production and DR. At the production site with have 3 VMware hosts using shared SAN storage. At the DR site we have 2 hosts using shared MSA storage. We have configured the MSA storage with 2 large datastores.

    We are replicating a number of VMs from the Production to the DR site. We have “balanced” those more or less evenly to each of the DR hosts (i.e. we have roughly half of them going to the first one and half going to the second one). Same thing on the storage: Roughly half to each of the 2 datastores at the DR site.

    The question is: What happens if one of the DR hosts goes down during a failover (i.e. when the DR site is “active”)? Since we are running on shared storage, the other host is able to “see” the VM files that were being managed by the first host, but will we be able to start them up on this other host (which we did not configure as being “responsible” for those VMs to begin with)?

    And what happens if a host goes down during day-to-day replication operations – can we press the other host into “taking care” of the first hosts VMs?

    We are only using VMware Essentials at the DR site, but can live with having to shut down VMs in order to vMotion them, if necessary.

    Br,
    Hans

    Bar A
    August 30, 2019 08:18:37 AM

    Hello Hans,

    In a case one of the DR hosts goes down during a failover, Zerto will rollback the VPG  automatically and then you should be able to edit the VPG (now it is in “need configuration state”) to point to a healthy host (with the relevant datastore exposed to it)  and failover again.

    With regards to the second question,

    Production scenario:

    In a case a host goes down at the production site, If there is HA feature on that vCenter, the HA will vMotion the VMs to another host, if that host has a VRA installed on replication will resume.

    A second option would be to fix the host/to bring the host back on, and replication should resume with delta sync.

    Best Regards,

     

    Hans K
    August 30, 2019 11:22:09 AM

    I guess I was not clear. In the first part of my question, my scenario is that we have performed a failover because an actual disaster has occured. So we can not fail back to reconfigure VPGs.

    In the second scenario, it is one of the two DISASTER RECOVERY hosts that has gone down. Assume that the three production hosts are okay.

    Try again, please 🙂

    Matthew W
    August 30, 2019 09:02:22 PM

    Hi there, Hans.

    At this time, Zerto does not support a host VRA picking up VMs from a failed host VRA during failover, as the situation you described. The VRAs are separate entities, and moving VMs between them would require both to be up and operational. If you would like to see this feature added, please submit a feature request at https://www.zerto.com/myzerto/support/feature-requests/. If you are concerned about a host going down during a recovery situation, you could also use the One To Many replication feature, to replicate a VM to two sites. They will need to be two sites, however, and not two hosts at one site.

    As to your second question, if a host goes down during day to day replication, you can change the recovery VRA using the below instructions (for Zerto 7.0 in a VMWare environment), but it will need to resync if the original VRA is down.

    http://s3.amazonaws.com/zertodownload_docs/Latest/Zerto%20Virtual%20Replication%20Zerto%20Virtual%20Manager%20%28ZVM%29%20-%20vSphere%20Online%20Help/index.html?cb=1567198835#page/AdministratorforZertoVirtualManager%2FManageVRA_VC.11.06.html

     

    I hope this helps!

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