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A full sync causes Storage DRS to trigger Storage vMotion only if you set the Storage DRS rules to be
very aggressive, or if a large number of virtual machines perform a full sync at the same time. The
default I/O latency threshold for Storage DRS is 15ms. By default, Storage DRS performs loading
balancing operations every 8 hours. Storage DRS also waits until it has collected sufficient statistics
about the I/O load before it generates Storage vMotion recommendations. Consequently, a full sync
only affects Storage DRS recommendations if the full sync lasts for a long time and if, during that time,
the additional I/O that the full sync generates causes the latency to exceed the I/O latency threshold.
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When you use Storage DRS in manual mode on protected virtual machine datastores, stale
recommendations might exist after a failover. After reprotecting the failed over virtual machines to the
original site, if you apply these stale Storage DRS recommendations, the Site Recovery Manager
placeholder VM becomes corrupted, causing a subsequent recovery to the original site to fail for the
VMs for which the Storage DRS recommendations were applied. If you apply stale updates, unregister
the placeholder VM and use the Site Recovery Manager repair operation to recreate a valid placeholder.
To avoid this issue, clear any stale recommendations from a prior failover from that site by regenerating
Storage DRS recommendations for the affected Storage DRS storage cluster after reprotect successfully
completes.
How Site Recovery Manager Interacts with vSphere High Availability
You can use Site Recovery Manager to protect virtual machines on which vSphere High Availability (HA) is
enabled.
HA protects virtual machines from ESXi host failures by restarting virtual machines from hosts that fail on
new hosts within the same site. Site Recovery Manager protects virtual machines against full site failures by
restarting the virtual machines at the recovery site. The key difference between HA and
Site Recovery Manager is that HA operates on individual virtual machines and restarts the virtual machines
automatically. Site Recovery Manager operates at the recovery plan level and requires a user to initiate a
recovery manually.
To transfer the HA settings for a virtual machine onto the recovery site, you must set the HA settings on the
placeholder virtual machine before performing recovery, at any time after you have configured the
protection of the virtual machine.
You can replicate HA virtual machines by using array-based replication or vSphere Replication. If HA
restarts a protected virtual machine on another host on the protected site, vSphere Replication will perform
a full sync after the virtual machine restarts.
Site Recovery Manager does not require HA as a prerequisite for protecting virtual machines. Similarly, HA
does not require Site Recovery Manager.
How Site Recovery Manager Interacts with Stretched Storage
Stretched storage support is available for array-based replication.
Site Recovery Manager supports active-active stretched storage between protected and recovery sites by
using Cross vCenter Server vMotion to perform planned migrations, eliminating service downtime. Disaster
recovery and test recovery continue to use the existing LUN-based recovery functionality.
IMPORTANT Stretched storage is supported only on vCenter Single Sign-On Enhanced Linked Mode
environments. Planned migration with Cross vCenter Server vMotion fails if the sites are not Enhanced
Linked Mode. Stretched storage is required when using Cross vCenter Server vMotion during a planned
migration.
Chapter 11 Interoperability of Site Recovery Manager with Other Software
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