Administrator Guide

Live Volume support for Microsoft Windows/Hyper-V
79 Dell EMC SC Series: Synchronous Replication and Live Volume | CML1064
Note: Each customer needs to make an informed choice about how they configure the quorum witness for a
clustered environment that utilizes LV-AFO. The risk of an outage due to a temporary loss of quorum due to a
less resilient design might be permissible in some cases, such as for test or development environments.
• Quorum witness: With Windows/Hyper-V clusters (physical or virtual), administrators can choose
between a SAN-based quorum disk witness or a file share witness to serve as a tiebreaker. This is
particularly important when there are equal numbers of nodes at each site, given a stretch cluster with
LV-AFO. Configuring a quorum witness with Windows Server 2012 R2 Hyper-V and newer is
recommended, regardless of the number of cluster nodes.
- The optimal quorum configuration for LV-AFO is a file share witness that is located at a third site
to ensure that the surviving node(s) at either site A or site B (given a complete site failure at either
location) always have continuous, uninterrupted access to the quorum. This is true for both
physical node clusters and guest VM clusters.
- If a third site is not available for a file share witness, then the next best configuration is to use a
SAN-based quorum disk that is also a Live Volume, configured for LV-AFO, so it can
automatically fail over given a DR situation.
However, this may not prevent loss of quorum given a complete site failure if the site that goes
down hosts the quorum disk (as a primary LV), and it also hosts the node that owns the quorum
disk. Given a complete site failure, if the quorum disk is configured for LV-AFO, it will fail over to
the other site and become available as a primary LV to a surviving node. However, with a
complete site failure, the combination of a surviving node needing to take ownership of the
quorum disk, concurrent with the short pause in I/O to the quorum disk (20 to 30 seconds) while
LV-AFO completes, may result in a failure of a surviving node to take ownership of the quorum
disk. If this occurs, workloads dependent on cluster resources at the surviving site may go offline
if the surviving nodes require a tiebreaker to achieve quorum, as would be the case if there are
an equal number of cluster nodes at each site. To avoid this scenario, configure a file share
witness at a third location.
- Configuring a file share witness that is local to either site A or site B given a stretch cluster
configuration with LV-AFO should be avoided. If the site that hosts the file share witness suffers a
site outage, access to the file share witness by the surviving nodes at the surviving site will fail. If
the file share witness is unavailable to the surviving nodes as a tiebreaker, and its vote is needed
to maintain quorum, then cluster resources will go offline.
Note: There are two additional methods of guest VM clustering that have not been tested with LV-AFO:
Windows Server guest VM clusters on Hyper-V that use pass-through disks, or virtual Fibre Channel disks as
cluster disks. While they may work, they are not supported configurations with LV-AFO.