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VMware vSphere Fault Tolerance

VMware Fault Tolerance (FT) is a new feature that is available with vSphere 4.0. VMware FT is based on vLockstep technology and aims to provide zero downtime, zero data loss, and continuous availability for applications. FT provides this continuous availability for applications by creating a secondary, live shadow instance of a virtual machine (VM) that is in virtual lockstep with the primary VM instance.

Next, VMware FT builds on VMware High Availability (HA). Therefore, HA has to be running correctly in order to enable FT. VMware FT can be turned on or off for individual virtual machines with a click of the mouse. In addition, since it leverages existing VMware HA clusters with a maximum node limit of 16 servers, any number of virtual machines in the cluster can be protected with VMware FT.

Finally, if you have set up VMware HA cluster and meet the Prerequisites and Requirements below, enabling FT is only a few mouse clicks away. Check out the step-by-step screen captures of enabling FT and testing failover with FT enabled at FT Example Down Below.

VMware vSphere FT Prerequisites

For VMware FT to perform as expected, it must run in an environment that meets specific requirements.

• The primary and secondary fault-tolerant virtual machines must be in a VMware HA cluster.
• Primary and secondary virtual machines must not run on the same host. FT automatically places the secondary virtual machine on a different host.
• Virtual machine files must be stored on shared storage.
• Shared storage solutions include NFS, FC, and iSCSI.
• For virtual disks on VMFS-3, the virtual disks must be thick, meaning they cannot be thin or sparsely allocated.
• Turning on VMware FT automatically converts the virtual machine to thick-eager zeroed disks.
• Virtual Raw Disk Mapping (RDM) is supported. Physical RDM is not supported.
• Multiple gigabit Network Interface Cards (NICs) are required.
• A minimum of two VMKernel Gigabit NICs must be dedicated to VMware FT Logging and vMotion.
• The FT Logging interface is used for logging events from the primary virtual machine to the secondary FT virtual machines.
• For best performance, use 10Gbit NIC rather than 1Gbit NIC, and enable the use of jumbo frames.
• VMware FT requires that Hardware Virtualization (HV) be turned on in the BIOS. The process for enabling HV varies among BIOSs. Contact your vendor for specifics.

VMware vSphere FT Requirements

There are a number of requirements which must be met before FT can be set up:

• CPUs: limited processors must be the same family (no mix/match).
• Requires Intel 31xx, 33xx, 52xx, 54xx, 55xx, 74xx or AMD 13xx,23xx, 83xx series of processors.
• SMP virtual machines are not supported.
• Hardware Virtualization must be enabled in the BIOS.
• Hosts must be in a VMware High Availability-enabled cluster.
• Storage: shared storage (FC, iSCSI, or NAS).
• Network: minimum of 3 NICs for various types of traffic (ESX Management/VMotion, virtual machine traffic, FT logging).
• GigE required for vMotion and FT logging.
• Minimized single points of failures in the environment. For example, NIC teaming, multiple network switches, storage multipathing.
• Primary and secondary hosts must be running the same build of ESX.

http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&externalId=1010601&sliceId=1&docTypeID=DT_KB_1_1&dialogID=29660642&stateId=1%200%2029664181

Guest Operating Systems

The following table displays guest operating system support for VMware FT. For specific guest operating system version information, see the Guest Operating System Installation Guide at http://www.vmware.com/pdf/GuestOS_guide.pdf.

The following values appear in the table:

• Yes - Virtual machine can be FT-enabled while powered on.
• Yes/Off - Virtual machine must be powered off before FT is enabled.
• No - Not supported by VMware FT.

Guest Operating System	Fault Tolerance Support with Intel Xeon Based on 45nm Core 2 Microarchitecture	Fault Tolerance Support with Intel Xeon Based on Core i7 Microarchitecture	Fault Tolerance Support with AMD 3rd Generation Opteron
Windows Server 2008	Yes	Yes/Off	Yes/Off
Windows Vista	Yes	Yes/Off	Yes/Off
Windows Server 2003 (64 bit)	Yes	Yes/Off	Yes/Off
Windows Server 2003 (32 bit)	Yes	Yes/Off	Yes/Off (Requires Service Pack 2 or greater)
Windows XP (64 bit)	Yes	Yes/Off	Yes/Off
Windows XP (32 bit)	Yes	Yes/Off	No
Windows 2000	Yes/Off	Yes/Off	No
Windows NT 4.0	Yes/Off	Yes/Off	No
Linux (all ESX-supported distributions)	Yes	Yes/Off	Yes/Off
Netware Server	Yes/Off	Yes/Off	Yes/Off
Solaris 10 (64-bit)	Yes	Yes/Off	Yes/Off (Requires Solaris U1)
Solaris 10 (32-bit)	Yes	Yes/Off	No
FreeBSD (all ESX-supported distributions)	Yes	Yes/Off	Yes/Off

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1008027

VMware vSphere FT Step by Step Example

1. Image depicting the Network configuration.




2. Turning on FT.



3. 54% through setting up FT.



4. FT setup complete.



5. vLockstep Interval and Log Bandwidth information are now updated.



6. Primary VM is located on 10.10.10.146.



7. Secondary VM is running on the Secondary Host- 10.10.10.145.



8. Testing FT using the built in Test Failover command.



9. Failover test completes. Notice that 10.10.10.146 has become the secondary location.



10. After the Failover Test, the primary host server is now 10.10.10.145 and the primary VM is running on it.



11. Furthermore, after the Failover Test, the secondary VM runs on the secondary host server, 10.10.10.146.



12. Failover test completion will result in showing the primary VM on the new primary host server and the new secondary host server with the accompanying vLockstep Interval and Log Bandwidth.



13. Finally, VMware vSphere FT is ready to provide continuous protection to your VMs.