How Does
VMware Fault Tolerance Work?
Using vLockstep Technology, VMware FT maintains a mirrored secondary VM
on a separated physical Host that is kept in the Lockstep with the primary VM.If the physical host on which the
primary VM fails, the secondary VM can immediately step in and take over
without any loss of connectivity. VMware FT can work in conjunction with
VMotion, but it cannot work with DRS
The primary and secondary virtual machines appear as a single entity
and access a common disk, both running with the single IP
address, Mac address but writes are only performed by the primary virtual
machine.
Version recap :
FT Technology :
Record/Replay
Record/Replay
works by recording the computer execution on a VM and saving it as a log file.
It can then take that recorded information and replay it on another VM .
Fast Checkpointing
It copies
active memory contents from Primary to Secondary via FT logging network on a
continuous basis and hence a 10G network is recommended.
What
is FT Logging Traffic?
FT logging is the one
of option in VMkernel port setting which is similar to enable vmotion option in
the vmkernel port. when FT is enabled for the virtual machine, all the inputs
(disk read.. wirte,etc..) of the primary virtual machine are recorded and
sent to the secondary VM over via FT logging enabled VMkernel port.
When you enable Fault Tolerance for the virtual machine, a secondary virtual machine (live shadow image of the primary) will be created to work with the primary virtual machine in which you have enabled FT. The primary and secondary virtual machine resides on a different ESX hosts in the cluster.
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