Both Storage Area Networks (SANs) and Network Attached Storage
(NAS) provide networked storage solutions.Answer: A NAS is a single
storage device that operate on data files, while a SAN is a local
network of multiple devices that operate on disk blocks. SAN vs NAS
TechnologyA SAN commonly utilizes Fibre Channel interconnects. A
NAS typically makes Ethernet and TCP/IP connections. SAN vs NAS
Usage ModelThe administrator of a home or small business network
can connect one NAS device to their LAN. The NAS maintains its own
IP address comparable to computer and other TCP/IP devices. Using a
software program that normally is provided together with the NAS
hardware, a network administrator can set up automatic or manual
backups and file copies between the NAS and all other connected
devices. The NAS holds many gigabytes of data, up to a few
terabytes. Administrators add more storage capacity to their
network by installing additional NAS devices, although each NAS
operates independently. Administrators of larger enterprise
networks may require many terabytes of centralized file storage or
very high-speed file transfer operations. Where installing an army
of many NAS devices is not a practical option, administrators can
instead install a single SAN containing a high-performance disk
array to provide the needed scalability and performance.
Administrators require specialized knowledge and training to
configure and maintain SANs. SAN / NAS ConvergenceAs Internet
technologies like TCP/IP and Ethernet have proliferated worldwide,
some SAN products are making the transition from Fibre Channel to
the same IP-based approach NAS uses. Also, with the rapid
improvements in disk storage technology, today's NAS devices now
offer capacities and performance that once were only possible with
SAN. These two industry factors have led to a partial convergence
of NAS and SAN approaches to network storage.
Network Attached Storage (NAS)The primary difference between NAS
and SAN solutions is the type of access protocol.
Network Attached Storage (NAS)Network Attached Storage (NAS)
devices are storage arrays or gateways that support file-based
storage protocols such as NFS and CiFS, and are typically connected
via an IP network. These file-based protocols provide clients
shared access to storage resources. This centralization of shared
storage resources reduces management complexity, minimizes stranded
disk capacity, improves storage utilization rates and eliminates
file server sprawl.NAS vs SANThe primary difference between NAS and
SAN solutions is the type of access protocol. NAS protocols such as
NFS and CiFS provide shared file level access to storage resources.
The management of the file system resides with the NAS device. SAN
protocols such as iSCSI and fibre channel provide block level
access to storage resources. Block level devices are accessed by
servers via the SAN, and the servers manage the file system.Despite
their differences, SAN and NAS are not mutually exclusive, and may
be combined in multi-protocol or unified storage arrays, offering
both file-level protocols (NAS) and block-level protocols (SAN)
from the same system. The best of both worlds!Benefits of NAS NAS
devices typically leverage existing IP networks for connectivity,
enabling companies to reduce the price of entry for access to
shared storage. The RAID and clustering capabilities inherent to
modern enterprise NAS devices offer greatly improved availability
when compared with traditional direct attached storage. Because NAS
devices control the file system, they offer increased flexibility
when using advanced storage functionality such as snapshots. With
10GE connectivity, NAS devices can offer performance on par with
many currently installed fibre channel SANsKey NAS UsesTraditional
use cases for NAS devices include file shares, home directories and
centralized logging. Recently, as the performance and availability
of NAS devices has improved, many customers are expanding the use
of NAS to include storage for relational databases such as Oracle
and MySQL, server virtualization environments such as VMWare
VSphere, and virtual desktop solutions such as VMWare VDI.Creating
a Network Attached Storage SolutionNAS is a common storage
infrastructure offering in data centers worldwide. Eastern Computer
has assisted many of our customers in justifying, designing, and
implementing enterprise NAS solutions we can do the same for you!
Along the way, we'll work with you to develop a solution that meets
your needs, allowing you to: Lower acquisition and management costs
Meet performance and availability requirements Handle ever
increasing annual storage growth with minimal, to no impact to your
business Minimize, or even eliminate the impact of backup windows
Deliver operational and disaster recoveryGrowing a Network Attached
Storage Network If your SAN has existed for a year or more, you are
more than likely struggling with the following questions: Should I
have a dedicated IP network for my NAS solution? What is the best
data protection solution for my NAS environment? Does it make sense
to use NAS storage with VMWare or HyperV? Is my NAS environment a
good candidate for de-duplication and compression of primary
storage? What options are available for archiving file system data?
What features are different among NAS vendors, and how will that
impact me? Should some of my data be on a NAS device, or never
aging iSCSI?Eastern Computer can help answer all your SAN growth
questions, and deliver an architecture that meets your business
needs.Customized NAS OfferingsGiven the breadth of use cases for
NAS devices, Eastern Computer can customize our NAS offerings to
meet your needs. Here are some of the services delivered to our
customer base: Complete Storage Audit A thorough analysis of your
current storage infrastructure, along with an architecture roadmap,
and ROI for investing in a SAN File System Assessment -- provides
vital information about server volumes and files in heterogeneous
storage networks without requiring installation of server agents.
Using EMC standard tools we can identify capacity utilization, file
age distribution, space consumption, last access time, last
modification time, duplicate file types, and perform a file type
classification. Once the analysis is complete, we present you with
reports, findings, and recommendations in easy to understand
format.This analysis can take as little time as an hour without
impact to your production environment with minimal input from your
IT administrators. Benefits: Helps in determining the aging of
files and how much content is not being accessed or modified.
Realize how much capacity can be reclaimed if this data were to be
moved to an archiving tier. Understand what type of data resides on
the servers. Single assessment that tells you all you need to know
about the data residing on your file servers. What is the
Difference between a Storage Area Network (SAN) Network Attached
Storage (NAS)Tue 02/15/11At first glance Network Attached storage,
also called NAS is not much different from a Storage Area Network
(SAN). They both attach to a network, they both provide storage to
computers on their network. There are some major differences
between the two storage roles. However, these two things are
becoming more and more the same thing.Differences in AppearanceThe
first thing to look at when debating if you are using a SAN or a
NAS is how the operating system sees the storage. Does the
operating system see the storage as being on a remote computer? Or
does the operating system see the storage as being local? If the
operating system and/or programs knows the storage is not local,
you are probably working with a NAS.
A good example of this is with Microsoft Windows network drives.
If you map a network drive in windows you get a drive letter, but
windows shows this drive as a network drive. Only the one user has
access to it, and windows will not let you use this drive for many
functions.
If you connect to a SAN Windows cant tell the storage is
actually somewhere on the network. It treats the storage as if it
was connected directly to the server. It is accessible to any user
logged into the system; and you can use it just like any other
drive.NAS ProtocolsWhen working with a SAN vs a NAS there are
different protocols involved. When you connect to a NAS you will
typically be working with Network Attached File Systems (NFS) or
Common Internet File Systems (CIFS). In Windows, if you map a
network drive to an NFS or CIFS volume, it will be treated as I
have stated above, it is usable by the one user, and you are
limited in what you can do.
In Linux/Unix network drives are treated differently. When you
mount an NFS or CIFS volume it is treated much like it was a local
disk and is available to all users on the system unless the file
system permissions do not allow it.SAN ProtocolsWhen working with a
SAN the most common protocols are iSCSI and Fiber Channel.
Typically when working with the iSCSI protocol you will operate
over an Ethernet network, and when working with Fiber Channel you
will operate over a fiber optic network. However, this is not
always the case. There is another protocol called Fiber Channel
over Ethernet (FCOE). And there is nothing stopping you from using
iSCSI over a fiber optic network.
FCOE operates a lot like iSCSI. iSCSI is an implementation of
the SCSI protocol where the SCSI operations are wrapped in a TCP
Packet and sent over the network. When the storage system receives
the TCP packet, it extracts the SCSI command and executes it on the
local storage. It then takes the result, wraps it in another TCP
packet it sends it back to the client machine. FCOE does the same
thing, only it uses the Fiber Channel protocol instead of the SCSI
protocol.How do they Operate?When working with NAS storage, the
client machine operates at the file level. This means when you want
to access mycoolpicture.jpg your computer sends a message the NAS
over the network asking for mycoolpicture.jpg, then the NAS
responds by sending the file. When using a SAN you are operating at
the block level.
This means the client machine cant simply ask for
mycoolpicture.jpg. The client machine needs to actually tell the
SAN where on the volume the file is. The operating system will send
a message to the SAN asking for specific blocks on the file system.
For example, if the picture is stored in blocks 5555 - 5577, then
the client system would ask for blocks 5555 - 5577, the SAN would
read those blocks, then send them over the network. The SAN does
not know what it is reading, it is simply following orders.Shared
access to a SAN or a NASDue to the nature of how a NAS works, it is
not a problem to connect multiple servers to the same share on your
NAS. You have to be more careful when connecting the same volume on
a SAN to more than one client system.
This limitation comes from the way the SAN operates. Since a NAS
shares files, the NAS device can handle things such as file locks
and consistency checking. A SAN operates at the block level, and
just trusts the operating system to know what it is doing with the
blocks. Unless your file system is setup to allow for simultaneous
access from more than one device you are asking for trouble.
For example, lets assume you have a SAN with a single volume,
and you connect it to two servers running Windows 2003 Standard.
Both systems see the volume and try to use it. When the first
server writes files to the system, everything works fine. Then the
other server modifies the files in some way, perhaps it just reads
the files and updates the date accessed attribute on the file. NTFS
is looking at the blocks of the file system and sees changes it did
not expect. NTFS at this point may think there is something wrong
with that Block and take some corrective action. At the same time
the other server will see something strange happening and take the
same action. In the end, you have a corrupt file.
Some file systems are designed for simultaneous access to the
same SAN volume, for example the VMWare File System (VMFS). In a
purely windows environment you want to make sure you never connect
the same SAN volume to more than one server at a time unless you
are using clustering.
When using Microsoft Clustering Services (MSCS) the cluster
service knows you have a volume connected to more than one server
and it ensures that the volume is only mounted on a single server
within the cluster at any given time; assuming it is properly
configured. This does not protect you from mounting that volume on
another server outside the cluster, which would be a bad
idea.Cluster Aware File SystemsAs I expressed in the previous
section, you have to be careful as to which file system you use
when sharing storage using iSCSI or similar protocols with more
than one server at a time. A cluster Aware File System allows you
to connect the file system to more than one server at a time.Below
is a list of a few cluster aware file systems:OCFS2 - Oracle
Cluster File system (Part of Linux Kernel)VMFS - VMWare File
SystemCXFS - Clustered XFSBelow is a list of File systems which I
know to not be cluster aware:NTFS - NT File SystemEXT2 - LinuxEXT3
- LinuxFat 16/32 - File Allocation Table (Used in Dos and
Windows)XFS - Linux
The above lists by no means cover every file system, but does
give a few examples of what you may be using. In a future article I
will go over some of the good and bad elements of different file
systems.
Difference between VMware ESX and ESXi 21:08 Mohammed Raffic
It's been a long debate that everyone has been asked by what is the
difference between ESX and ESXi. Most of the admins would have
asked this question during interviews and also asked by new
learners of VMware virtualization. I decided to post on the topic
to give architectural difference always as to compare the different
level capabilities between ESX & ESXi. What is VMware ESX ?
ESX (Elastic Sky X) is the VMwares enterprise server
virtualization platform. In ESX, VMkernel is the virtualization
kernel which is managed by a console operating system which is also
called as Service console. Which is linux based and its main
purpose is it to provide a Management interface for the host and
lot of management agents and other thrid party software agents are
installed on the service console to provide the functionalists like
hardware management and monitoring of ESX hypervisor. Graphic
Thanks to VMware
What is VMware ESXi ?
ESXi (Elastic sky X Integrated) is also the VMwares enterprise
server virtualization platform. In ESXi, Service console is
removed. All the VMware related agents and third party agents such
as management and monitoring agents can also run directly on the
VMkernel. ESXi is ultra-thin architecture which is highly reliable
and its small code-base allows it to be more secure with less codes
to patch. ESXi uses Direct Console User Interface (DCUI) instead of
a service console to perform management of ESXi server. ESXi
installation will happen very quickly as compared to ESX
installation.
Graphic Thanks to VMware
Difference between ESX and ESXiESX 4.1 is the last version
availability of ESX server. After vSphere 5, only ESXi is
available. This comparison based out of the VMware Article
CapabilityESX ESXi
Service ConsolePresentRemoved
Troubleshooting performed viaService Console ESXi Shell
Active Director AuthenticationEnabledEnabled
Secure Syslog Not SupportedSupported
Management NetworkService Console InterfaceVMKernel
Interface
Jumbo FramesSupported Supported
Hardware Montioring3 rd Party agents installed in Service
consoleVia CIM Providers
Boot from SANSupported in ESXSupported in ESXi
Software patches and updatesNeeded as smilar to linux operation
systemFew pacthes because of small footprint and more secure
vSphere web AccessOnly experimentalFull managenet capability via
vSPhere web client
Locked Down ModeNot presentPresent . Lockdown mode prevents
remote users to login to the host
Scripted InstalltionSupportedSupported
vMA SupportYesYes
Major Administration command-line Commandesxcfg-esxcli
Rapid deployment via Auto DeployNot supportedSupported
Custom Image creationNot supportedSupported
VMkernel Network Used for vMotion,Fault Tolarance,Stoarge
ConnectivityManagement Network , vMotion, Fault Tolarance, Stoarge
Connectivity, ISCSI port binding
VMWare interview questions and answers - HA (High Availability)
23:03 Mohammed Raffic
What is VMware HA?
As per VMware Definition,VMware High Availability (HA) provides
easy to use, cost effective high availability for applications
running in virtual machines. In the event of server failure,
affected virtual machines are automatically restarted on
otherproduction servers with spare capacity
What is AAM in HA?
AAM is the Legato automated availability management. Prior to
vSphere 4.1, VMware's HA is actually re engineered to work with
VM's with the help of Legato's Automated Availability Manager (AAM)
software. VMware's vCenter agent (vpxa) interfaces with the VMware
HA agent which acts as an intermediary to the AAM software. From
vSphere 5.0, it uses an agent called FDM (Fault Domain
Manager).
What are pre-requites for HA to work?
1.Shared storage for the VMs running in HA cluster2.Essentials
plus, standard, Advanced, Enterprise and Enterprise Plus
Licensing3.Create VMHA enabled Cluster4.Management network
redundancy to avoid frequent isolation response in case of
temporary network issues (preferred not a requirement)
What is maximum number of primary HA hosts in vSphere 4.1?
Maximum number of primary HA host is 5. VMware HA cluster
chooses the first 5 hosts that joins the cluster as primary nodes
and all others hosts are automatically selected as secondary
nodes.
How to see the list of Primary nodes in HA cluster?
View the log file named "aam_config_util_listnodes.log" under
/var/log/vmware/aam using the below command
cat /var/log/vmware/aam/aam_config_util_listnodes.log
What is the command to restart /Start/Stop HA agent in the ESX
host?
service vmware-aam restart
service vmware-aam stop
service vmware-aam start
Where to located HA related logs in case of troubleshooting?
/Var/log/vmware/aam
What the basic troubleshooting steps in case of HA agent install
failed on hosts in HA cluster?
Below steps are are taken from my blog posts Troubleshooting
HA
1. Check for some network issues
2. Check the DNS is configured properly
3. Check the vmware HA agent status in ESX host by using below
commands
service vmware-aam status
4. Check the networks are properly configured and named exactly
as other hosts in the cluster. otherwise, you will get the below
errors while installing or reconfiguring HA agent.
5. Check HA related ports are open in firewall to allow for the
communication Incoming port: TCP/UDP 8042-8045 Outgoing port:
TCP/UDP 2050-2250
6. First try to restart /stop/start the vmware HA agent on the
affected host using the below commands. In addition u can also try
to restart vpxa and management agent in the Host.
service vmware-aam restart
service vmware-aam stop
service vmware-aam start
7. Right Click the affected host and click on "Reconfigure for
VMWare HA" to re-install the HA agent that particular host.
8. Remove the affected host from the cluster. Removing ESX host
from the cluster will not be allowed untill that host is put into
maintenance mode.
9.Alternative solution for 3 step is, Goto cluster settings and
uncheck the vmware HA in to turnoff the HA in that cluster and
re-enable the vmware HA to get the agent installed.
10. For further troubleshooting , review the HA logs under
/Var/log/vmware/aam directory.
What is the maximum number of hosts per HA cluster?
Maximum number of hosts in the HA cluster is 32
What is Host Isolation?
VMware HA has a mechanism to detect a host is isolated from rest
of hosts in the cluster. When the ESX host loses its ability to
exchange heartbeat via management network between the other hosts
in the HA cluster, that ESX host will be considered as a
Isolated.
How Host Isolation is detected?
In HA cluster, ESX hosts uses heartbeats to communicate among
other hosts in the cluster.By default, Heartbeat will be sent every
1 second.
If a ESX host in the cluster didn't received heartbeat for for
13 seconds from any other hosts in the cluster, The host considered
it as isolated and host will ping the configured isolation
address(default gateway by default). If the ping fails, VMware HA
will execute the Host isolation response
What are the different types isolation response available in
HA?
Power off All the VMs are powered off , when the HA detects that
the network isolation occurs
Shut down All VMs running on that host are shut down with the
help of VMware Tools, when the HA detects that the network
isolation occurs.If the shutdown via VMWare tools not happened
within 5 minutes, VM's power off operation will be executed. This
behavior can be changed with the help of HA advanced options.
Please refer my Post on HA Advanced configuration
Leave powered on The VM's state remain powered on or remain
unchanged, when the HA detects that the network isolation
occurs.
How to add additional isolation address for redundancy?
By default, VMWare HA use to ping default gateway as the
isolation address if it stops receiving heartbeat.We can add an
additional values in case if we are using redundant service console
both belongs to different subnet.Let's say we can add the default
gateway of SC1 as first value and gateway of SC2 as the additional
one using the below value
1. Right Click your HA cluster
2. Goto to advanced options of HA
3. Add the line "das.isolationaddress1 = 192.168.0.1"
4. Add the line "das.isolationaddress2 = 192.168.1.1" as the
additional isolation address
To know more about the Advanced HA Options
What is HA Admission control?
As per "VMware Availability Guide",
VCenter Server uses admission control to ensure that sufficient
resources are available in a cluster to provide failover protection
and to ensure that virtual machine resource reservations are
respected.
What are the 2 types of settings available for admission
control?
Enable: Do not power on VMs that violate availability
constraints
Disable: Power on VMs that violate availability constraints
What are the different types of Admission control policy
available with VMware HA?
There are 3 different types of Admission control policy
available.
Host failures cluster toleratesPercentage of cluster resources
reserved as fail over spare capacitySpecify a fail over host
How the Host Failures cluster tolerates admission control policy
works?
Select the maximum number of host failures that you can afford
for or to guaranteefail over. Prior vSphere 4.1, Minimum is 1 and
the maximum is 4.
In the Host Failures cluster tolerates admission control policy
, we can define the specific number of hosts that can fail in the
cluster and also it ensures that the sufficient resources remain to
fail over all the virtual machines from that failed hosts to the
other hosts in cluster. VMware High Availability(HA) uses a
mechanism called slots to calculate both the available and required
resources in the cluster for a failing over virtual machines from a
failed host to other hosts in the cluster.
What is SLOT?
As per VMWare's Definition,
"A slot is a logical representation of the memory and CPU
resources that satisfy the requirements for any powered-on virtual
machine in the cluster."
If you have configured reservations at VM level, It influence
the HA slot calculation. Highest memory reservation and highest CPU
reservation of the VM in your cluster determines the slot size for
the cluster.
How the HA Slots are Calculated?
I have written a post about how the HA slots are calculated.
How to Check the HA Slot information from vSphere Client?
Click on Cluster Summary Tab and Click on "Advanced Runtime
Info" to see the the detailed HA slotsinformation.
What is use of Host Monitoring status in HA cluster?
Let's take an example, you are performing network maintenance
activity on your switches which connects your one of th ESX host in
HA cluster.
what will happen if the switch connected to the ESX host in HA
cluster is down?
It will not receive heartbeat and also ping to the isolation
address also failed. so, host will think itself as isolated and HA
will initiate the reboot of virtual machines on the host to other
hosts in the cluster. Why do you need this unwanted situation while
performing scheduled maintenance window.
To avoid the above situation when performing scheduled activity
which may cause ESX host to isolate, remove the check box in "
Enable Host Monitoring" until you are done with the network
maintenance activity.
How to Manually define the HA Slot size?
By default, HA slot size is determined by the Virtual machine
Highest CPU and memory reservation. If no reservation is specified
at the VM level, default slot size of 256 MHZ for CPU and 0 MB +
memory overhead for RAM will be taken as slot size. We can control
the HA slot size manually by using the following values.
There are 4 options we can configure at HA advanced options
related to slot size
das.slotMemInMB - Maximum Bound value for HA memory slot
sizedas.slotCpuInMHz - Maximum Bound value for HA CPU slot
Sizedas.vmMemoryMinMB - Minimum Bound value for HA memory slot
sizedas.vmCpuMinMHz - Minimum Bound value for HA CPU slot size
For More HA related Advanced options, Please refer my blog
post
How the "Percentage of cluster resources reserved as failover
spare capacity" admission control policy works?
In the Percentage of cluster resources reserved as failover
spare capacity admission control policy, We can define the specific
percentage of total cluster resources are reserved for failover.In
contrast to the "Host Failures cluster tolerates admission control
policy", It will not use slots. Instead This policy calculates the
in the way below
1.It calculates the Total resource requirement for all
Powered-on Virtual Machines in the cluster and also calculates the
total resource available in host for virtual machines.2.It
calculates the current CPU and Memory Failover capacity for the
capacity.3.If the current CPU and Memory Failover capacity for the
cluster < configured failover capacity (ex 25 %)4.Admission
control will not allow to power on the virtual machine which
violates the availability constraints.
How the "Specify a failover host" admission control policy
works?
In the Specify a failover host" admission control policy, We can
define a specific host as a dedicated failover host. When isolation
response is detected, HA attempts to restart the virtual machines
on the specified failover host.In this Approach, dedicated failover
hist will be sitting idle without actively involving or not
participating in DRS load balancing.DRS will not migrate or power
on placement of virtual machines on the defined failover host.
What is VM Monitoring status?
HA will usually monitors ESX hosts and reboot the virtual
machine in the failed hosts in the other host in the cluster in
case of host isolation but i need the HA to monitors for Virtual
machine failures also. here the feature called VM monitoring status
as part of HA settings.VM monitoring restarts the virtual machine
if the vmware tools heartbeat didn't received with the specified
time using Monitoring sensitivity.
If you are looking for more VMware interview questions Please
click Interview Questions.
Thanks For Reading!!! All the Best...Posted in: High
Availability, Interview questions Email This BlogThis! Share to
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What is VMware Fault Tolerance?
VMware Fault Tolerance is a component of VMware vSphere and it
provides continuous availability to applications by preventing
downtime and data loss of Virtual machines in the event of ESX
serverfailures.
What is the name of thetechnologyused by VMware FT?
VMware FT using a technology called vLocksteptechnology
What are requirements and Limitattions for ESX hosts &
infrastructure components to run FT protected virtual machines in
Vsphere 4 & 4.1?
Please refer my blog post onESX Host -Infrastrcuture
Requirements & Limitations for VMware Fault Toleranceto see the
ESX requirements for VMware FT.
What are Requirements and Limitations for Virtual Machine to
Enable FT ?
Please refer myblog postonVirtual Machine Requirements for
VMware Fault Tolerance
How do i check my host for FT compatibility from vSphere
client?
One way from vSphere client is to run the cluster complaince
check from profile compliance tab of your cluster. The below checks
as specified below will be performed as part of the compliance
check.
Validate that Fault Tolerancelogging NIC speed is at least 1000
Mbps.Validate that power management is supported on the
hostValidate that Fault Tolerance logging is enabled.Validate that
VMotion NIC speed is at least 1000 Mbps.Validate that all the hosts
in the cluster have the same build for Fault ToleranceValidate that
the host hardware supports Fault Tolerance.Validate that VMotion is
enabled.Validate that at least one shared datastore exists
Another way is to check the summary tab of the ESX/ESXi host,
"Host Configured for FT" yes or NO.
If " Host Configured for FT" is No. It will display the items
required for thatparticularESX for FT to work.
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 thesecondaryVM over via FT logging enabled VMkernel
port.
How to Enable FT Logging in VMkernel Port?
GO the ESX host -> Configuration-> Networking ->
Properties of Virtual switch with the VMkernel portgroup
configured
Click on VMkernel Port -> click on Edit -> General tab
-> select the Fault Tolerance Logging -> click on OK.
How do you configure or enable FT for the virtual machine ?
FT can be enabled only per virtual machine basis not at the
cluster or ESX level.
Right-click the virtual Machine -> Fault Tolerance -> Turn
on Fault Tolerance
How does the FT enabled virtual machine will be differentiated
with non FT VM's in vSphere client?
FT Enabled Virtual machine will appear in Dark Blue colour as
compared to non-protected virtual machines.
By default, Only Primary virtual machine will appear under the
cluster and ESX host. To take a look at the secondary VM , Go to
Virtual Machines tab of the Cluster or Host.
How Does VMware Fault Tolerance Work?
When you enable Fault Tolerance for the virtual machine, a
secondary virtual machine 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. Whatever the events or actionsperformed by the primary VM
will be transmitted via gigabitEthernetnetwork to be replayed by
the secondary virtual machine using VLockstep technology.
Eventhough both the primary and secondary virtual machines appear
as a single entity and access acommon disk, both running with the
single IP address, MAc address but writes are only performed by the
primary virtual machine.The primary and secondary virtual machines
sends heartbeat between eachother frequently with millisecond
intervals to the check for the availability. If either of the
virtual machine loses the heartbeat, other virtualmachinewill take
over the primary virtual machine role immediately.
GraphicsThanks toVMware.com
What happens when you enabled Fault Tolerance for your virtual
machine?
When you enable Fault Tolerance for the virtual machine,
asecondaryvirtual machine (live shadow image of the primary) will
be created to work with the primary virtual machine in which you
haveenabled FT. The primary and secondary virtual machine resides
on a different ESX hosts in the cluster.
What will happen when the ESX host of primary VM failed?
When a failure is detected on the primary VM's ESX host, the
secondary virtual machine which is running on the another ESX
server in the same cluster will takes the place of the first one
with theleast possible interruption of service.
If vCenter is down, will the FT work?vCenter server is only
required to enable FT on the virtual machine.once it is configured,
vCenter is not required to be in online for FT to work. FT failover
between primary and secondary willoccure even if the vCenter is
down.
How does Vmware FT differs from VMware HA?
1.VMware HA is enabled per cluster basis but FT is enabled per
VM basis.
2.In caseof ESX host failure, virtual machines in the failed
host are restarted and powered-on on the other active hosts in HA
cluster. So the restart duration of the virtual machine is the
downtimefor the virtual machine in HA cluster. But in FT enabled
virtual machine, there is nodowntime. In case of host failure,
secondary VM will become primary and continuing the execution from
the exactpoint where the primary VM is left off or failed. It
happens automatically without data loss, without downtime and with
a little delay. Users will not see any interruption.
How do you see the summary status of the FT enabled virtual
machines in the ESX host from vsphere client?
Click on Summary tab of the ESX host -> Fault tolerance
information and VM counts will be displayed
ESX is an installed software suite managed by VirtualCenter by a
standalone VirtualCenter Client via a built-in VLI or web service.
ESX is licensed per seat and also has to have an agent license for
connecting to the VC server.ESXi is a free product that can be
installed on a server's disk or embedded by a flash device. It can
be managed by a VC Client or you can connect it to a VC Server.The
Major difference is that ESX has a Service Console (SC) for
management. ESXi does not have a service console and is much
smaller and more secure.ESXi management is GUI only where as ESX
management can be GUI or CLI based.