Mastering Windows Server 2016 Hyper-V

Now that you understand how to view the ongoing health of your Hyper-V Replica
environment, you can look at the types of failover that you want to perform with
Hyper-V Replica. Three types of failover are used with Hyper-V Replica, as detailed
here. Depending on its type, the failover is triggered from either the primary or replica
Hyper-V host by selecting one of the failover actions from the Replication action
menu.

Test    Failover    This    is  triggered   on  the replica virtual machine,    which   allows  the

replica VM  to  be  started on  the replica Hyper-V host    by  creating    a   temporary

virtual machine based   on  the recovery    point   selected.   Testing is  performed   to

ensure  that    replication is  working as  planned and as  part    of  a   larger  site    failover

test    process.    During  the test    failover,   the primary VM  continues   to  send    log

updates to  the replica VM, which   are merged  into    the replica VHDs,   ensuring    that

replication continues.  Once    testing is  complete,   the temporary   virtual machine is

deleted.    When    triggering  the test    failover,   you have    the option  to  select  the point   in

time    to  use for the failover    if  the virtual machine was enabled to  store   multiple

points  in  time    when    replication was enabled,    as  shown   in  Figure  8.7.    The test

failover    virtual machine is  not connected   to  the regular network to  avoid

interfering with    normal  network communications.

Figure  8.7 Selecting   the point   in  time    for the test    failover

Planned Failover    This    is  triggered   on  the primary virtual machine and is  the

preferred   failover    type.   This    process shuts   down    the primary VM, replicates  any

pending changes to  ensure  no  data    loss,   fails   over    to  the replica VM, reverses    the

replication (if the option  is  selected)   so  that    changes flow    in  the reverse direction,

and then    starts  the replica VM, which   becomes the primary (while  the old primary

becomes the replica).   Figure  8.8 shows   the options for the planned failover    that

include whether replication should  be  reversed    and whether the virtual machine

should  be  started on  the replica side.   You should  enable  the reversal    of  replication

unless  there   is  a   specific    reason  not to  do  so, such    as  if  you are using   extended

replication (this   will    be  discussed   later   in  this    section).   Note    that    even    though  this

is  a   planned failover,   the virtual machine is  still   shut    down    during  the failover,