Vmware DR

Posted on 2011-04-26
Last Modified: 2012-05-11

I am currently working on a DR setup for my vmware environment. What I have;

2* HP EVA sans
x* ESXi 4.1 installations
1* vCenter

The SANs are set up with synchronous mirroring from the primary site to the DR site. There are no "smart" devices in front of the SAN except for FC switches. The plan is running everything 100%/0% and should the primary site go down the DR site will become active.

I have thought of a few ideas such as adding the DR hosts to the vCenter installations(should I have 2?). Since the SAN does all the syncing of data, I could basically just make the DR hosts see the same datastores as the hosts in the primary site, but on the DR SAN and not the primary SAN?

Will for example a DR host connected to the DR SAN(including a few datastores) understand that the primary host connected to the primary SAN(including a few datastores) sees the same datastore or will they be "confused" because of differences on LUN's etc?

I have had a look on vmware SRM, but I am not sure whether I need that application or not.

I assume that if I had a device in front of the SAN that said "Hi, you dont need to know what SAN you are talking to - I am doing that work and it doesn't matter if you connect to the primary or DR san" would make it easier for hosts to understand(reference to IBM storage volume controller".

Anyone here with ideas on how these things work? As you may have noticed I am not much of a SAN technician, so I would very much appreciate your thoughts.

Thank you.
Question by:synackrst
    LVL 116

    Expert Comment

    by:Andrew Hancock (VMware vExpert / EE MVE)
    I would treat the Hosts in at the Primary Site and DR Site seperately.

    (if the link between Primary and DR site is fast enough).

    You can safely add them all to vCenter, and create two datacentres.

    Primary Site - ESX Hosts. - Primary SAN

    DR Site - ESX Hosts - DR SAN

    Primary SAN to DR Site SAN are mirroring.

    The present the LUNs (datatores) to ESX hosts in Primary Site.

    Present the (mirrored) LUNs (datastores) using same LUN Numbers to Hosts in DR Site.

    If you've got realtime mirroring in operation, you may not be able to present the LUNs (DR site) to ESX, without breaking the MIRRORS.

    Author Comment

    aha, how would a possible DR failover work should the primary site go down with the following configuration(same LUN numbers to the datastores on both sites)?
    If I am not mistaken there is a 4gbit redundant FC link and 1gbit ethernet link between the sites.

    Primary Site - ESX Hosts. - Primary SAN
    DR Site - ESX Hosts - DR SAN
    add them all to vCenter, and create two datacentres.

    Author Comment

    Also, I am not sure if there is only a one-way meaning primary to DR mirror or if the SAN data is mirrored both ways.
    LVL 116

    Expert Comment

    by:Andrew Hancock (VMware vExpert / EE MVE)
    the connection of hosts is to one san only.

    so the hosts and sans on both sites are separate.

    if primary site goes down, esx hosts and san at dr site are in use.

    Now on area you need to consider is networking at DR site is it the same as production?
    LVL 116

    Expert Comment

    by:Andrew Hancock (VMware vExpert / EE MVE)
    normally SAN mirroring is one way from primary to secondary site.


    Author Comment

    As no production is to run on the DR site a reroute of traffic should be OK afaik so that we can keep the same subnets etc, what I really would like to get some more information regarding is the routine that follows should the primary site crash'n'burn.
    Will I need to migrate all the virtual machines from the crashed hosts to the servers on the DR site manually? What if vCenter is down? Do you know?
    LVL 116

    Accepted Solution

    What is often done, is the Production Network is extended via VLAN to DR site, (this makes it much easier, should you need to enact a DR situation, otherwise you would have to change the IP addresses of all your production servers, this is why I ask, because this is what VMware SRM, can do for you but, if you can extend your production network to DR site, all the better, tick in the box, you've got that covered).

    You will need to check if this is how your scernaio is setup.

    If you have two SANS (SAN A (Production) and SAN B (DR)), currently at production you have


    ESX Hosts at Production connected to SAN A.
    Virtual Centre Server (is this Virtual or Physical)
    SAN A (LUNs containing datastores, containing VMs).

    DR Site

    ESX Hosts at DR Site connected to SAN B.
    SAN B (Mirrored LUNs containing the same datastores from SAN A, containing VMs).
    Server installed with vCenter or Workstation with vSphere GUI Client.

    In the event of Production Site disappearing.

    At the DR Site

    1. Your LUNs will already be available (as they've been mirrored).
    2. ESX servers are alrready conencted to SAN B.
    3. You may have to break the Mirror between SAN B and SAN A. (because the LUNs may be read only, locked because they are being written to).
    4. Connect to ESX hosts using vSphere Client to ESX hosts, rescan hbas, ESX hosts will discover all the datastores.
    5. Manually add servers to inventory.
    6. Power VMs.

    DR Site up and running. (this is in simplest terms).


    Author Closing Comment

    Thank you so much for your assistance. I will review and see what we end up doing. Cheers
    LVL 116

    Expert Comment

    by:Andrew Hancock (VMware vExpert / EE MVE)
    Good Luck, and remember the Experts are always here waiting for your questions.

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