What is the difference between Thick provision Lazy Zeroed, Thick provision Eager Zeroed and Thin provision?
Thick Provision Lazy Zeroed
Creates a virtual disk in a default thick format.
Space required for the virtual disk is allocated when the virtual disk is created.
Data remaining on the physical device is not erased during creation, but is zeroed out on demand at a later time on first write from the virtual machine.
Using the default flat virtual disk format does not zero out or eliminate the possibility of recovering deleted files or restoring old data that might be present on this allocated space.
You cannot convert a flat disk to a thin disk.
Thick Provision Eager Zeroed
A type of thick virtual disk that supports clustering features such as Fault Tolerance.
Space required for the virtual disk is allocated at creation time.
In contrast to the flat format, the data remaining on the physical device is zeroed out when the virtual disk is created.
It might take much longer to create disks in this format than to create other types of disks.
It provides on on-demand allocation of blocks of data.
All the space allocated at the time of creation of virtual disk is not utilized on the hard disk, rather only the size with utilized data is locked and the size increases as the amount of data is increased on the disk.
With thin provisioning, storage capacity utilization efficiency can be automatically driven up towards 100% with very little administrative overhead
. What is VMware Fault Tolerance?
VMware Fault Tolerance provides continuous availability to applications running in a virtual machine, preventing downtime and data loss in the event of server failures.
VMware Fault Tolerance, when enabled for a virtual machine, creates a live shadow instance of the primary, running on another physical server.
The two instances are kept in virtual lockstep with each other using VMware vLockstep technology
The two virtual machines play the exact same set of events, because they get the exact same set of inputs at any given time.
The two virtual machines constantly heartbeat against each other and if either virtual machine instance loses the heartbeat, the other takes over immediately. The heartbeats are very frequent, with millisecond intervals, making the failover instantaneous with no loss of data or state.
VMware Fault Tolerance requires a dedicated network connection, separate from the VMware VMotion network, between the two physical servers.
How many virtual CPUs can I use on a Fault Tolerant virtual machine ?
vCenter Server 4.x and vCenter Server 5.x support 1 virtual CPU per protected virtual machine.
what happens if vCenter Server is offline when a failover event occurs?
When Fault Tolerance is configured for a virtual machine, vCenter Server need not be online for FT to work. Even if vCenter Server is offline, failover still occurs from the Primary to the Secondary virtual machine. Additionally, the spawning of a new Secondary virtual machine also occurs without vCenter Server.
24. How is a Master host elected in vSphere HA environment?
When vSphere HA is enabled for a cluster, all active hosts (those not in standby or maintenance mode, or not disconnected) participate in an election to choose the cluster's master host. The host that mounts the greatest number of datastores has an advantage in the election. Only one master host typically exists per cluster and all other hosts are slave hosts.
If the master host fails, is shut down or put in standby mode, or is removed from the cluster a new election is held.
14. What is promiscuous mode in VMware?
If the promiscuous mode set to Accept, all the communication is visible to all the virtual machines, in other words all the packets are sent to all the ports on vSwitch
If the promiscuous mode set to Reject, the packets are sent to intended port, so that the intended Virtual machine was able to see the communication.