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Showing posts with the label VMware

VMware and Windows Interview Questions: Part 9

How can I change the EVC mode of an existing cluster?You need to shutdown all running VMs in that cluster to change the EVC modeWhat if reconnecting the ESXi host back to an EVC cluster fails?Make a note of the VM foldersRemove the ESXi host from the inventoryAdd the ESXi host directly to the vCenter outside the EVC clusterNow move the server to the EVC clusterAdd the VMs back to the foldersWhat is PSC?PSC is Platform Service ControllerThis is an extended SSO model which was there in pre 6.0 versionsIt takes care of authentication,licensing,certificates etc..What are the two deployment models of PSC?Embedded & ExternalEmbedded if PSC is installed in vCenter boxExternal if PSC is installed outside vCenter in separate boxHow can I check if storage is VAAI capable?Check datastore and confirm if it supports Hardware AccelerationWhat is vmx~?In addition to the normal vmx file, from vSphere 6.0 onwards there is an additional file vmx~vmx~ first takes any configuration changes and then w…

VMware and Windows Interview Questions: Part 5

1.What’s the number of permitted unsuccessful logons for Administrator account? a.Unlimited - Only for Administrator, not for others in Administrators group 2.Difference between Everyone and Authenticated users? a.Authenticated Users - Include all Users and Computers whose identities have been authenticated. b.Everyone - For Windows 2003 and above, 'Everyone' includes all Authenticated Users including Guest accounts. Before Windows 2003, 'Everyone' includes all Authenticated Users , Guest accounts and Anonymous account. 3.How many passwords by default are remembered when you check “Enforce Password History Remembered”? a.24 4.What is an IP Helper address feature and why is it required in a DHCP environment ? a.IP helper-address helps to implement DHCP relay agent in Cisco routers b.This is configured at the network interface of the router containing the DHCP client c.The IP helper-address intercepts the DHCP discover message from the client and unicasts it to the DHCP server aft…

VMware and Windows Interview Questions: Part 6

1.Can we setup an AD site  without a DC ? a.Yes.. 2.What is DAS ? How is it connected to the server ? a.DAS is Direct Attached Storage. DAS is available with many vendors. When a server has exhausted all its storage resource, we can connect a DAS solution to it. DAS can be connected to a server using SAS cable. 3.How is an iscsi device connected to a server ? a.An iscsi device can be connected using the iqn number. 4.How can I add new HDD space to an existing drive ? a.Convert the drive from Basic to Dynamic 5.What happens when a standalone host is taken into maintenance mode ? a.The activity will wait until all VMs are shutdown. 6.What if all GC in the environment are down ? a.GC is required for multi domain forests - In a single domain infrastructure, the DCs will not contact the GC for authenticating. But in multi domain infrastructure, GC is required for authentication. b.Universal Group Membership evaluation - Universal Group Membership which exists in a multi domain forests works only with …

VMware and Windows Interview Questions: Part 8

1.Can you map a single physical NIC to multiple virtual switches ? oNo 2.Can you map a single virtual switch to multiple physical NICs? oYes. This method is called NIC teaming. 3.In vSphere 5.5, VMKernel portgroup can be used for: ovMotion oFault Tolerance Logging oManagement traffic 4.Major difference between ESXi 5.1 and ESXi 5.5 (above) free versions oTill ESXi 5.1 free version there was a limit to the maximum physical memory to 32 GB. But from 5.5 onwards this limit has been lifted. 5.What is IPAM server in Windows server 2012? o IPAM is IP Address Management server in Windows Server 2012. It enables central management of both DHCP and DNS servers. It can also be used to discover, monitor, and audit DHCP and DNS servers. 6.How to promote a server to domain controller in Windows server 2012? oDCPROMO was the conventional tool used to promote a normal server to DC. This is now deprecated in Server 2012.  oIn Server 2012, you can convert a server into DC using the server manager console. Under Ser…

VMware and Windows Interview Questions: Part 7

1.Which networking features are recommended while using iSCSI traffic oiSCSI port binding oJumbo Frames 2.Ports used by vCenter o80,443,902 3.What is 'No Access' role oUsers assigned with the 'No Access' role for an object, cannot view or change the object in any way 4.When is a swap file created oWhen the guest OS is first installed in the VM 5.The active directory group, where the members will be ESXi administrators by default. oESX Admins 6.Which is the command used in ESXi to manage and retrieve information from virtual machines ? ovmware-cmd 7.Which is the command used in ESXi to view live performance data? oesxtop 8.Command line tool used in ESXi to manage virtual disk files? ovmkfstools 9.Port used for vMotion o

ESXi Maintenance mode improvements | VMware

Normally when an ESXi host is placed into maintenance mode, all the Powered On VMs will be migrated first to the other hosts in the cluster using DRS, then comes Powered Off VMs and finally VM templates.
Starting from vSphere 6.0 u2, VMware has changed the order. Now when a host is placed into maintenance mode, first the Powered Off VMs will be moved, then VM templates and finally the Powered On VMs.
Reason for change:

Prior to 6.0 U2, when users initiate Maintenance mode in ESXi, they lose the ability to deploy VMs using the templates until the migration completes. Even though the templates are migrated in the last place, ESXi host would have already queued the VM Templates and Powered Off VMs in its migration process. When we consider hosts with 40-50 VMs, users might need to wait for some time to work with the templates or to Power On a VM. Therefore VMware decided to make this small change which might turn useful to administrators atleast at some point of time.

VMware ESXi Memory State

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Memory state of an ESXi shows how much memory constrained the host is.
There are 5 memory states and depending on each memory state, ESXi will engage its memory reclamation techniques (TPS, Ballooning, Compression & Swapping).
High state: No reclamationClear state: TPSSoft state: TPS + BallooningHard state: TPS + Compression + SwappingLow state: TPS + Compression + Swapping + Blocking
How ESXi calculates its memory state ?
Memory state is not calculated using its overall utilization. But by comparing the current utilization with a dynamic  minFree value. Based on this comparison, ESXi changes its state.
High state : enough free memory availableClear state : <100% of minFreeSoft state : <64% of minFreeHard state : <32% of minFreeLow state : <16% of minFree
What is minFree value ?
minFree value is calculated using the configured memory of ESXi host. An ESXi host configured with 28GB RAM will have 899 MB as its minFree value. Any host configured wit…

ALUA & VMware multipating

What is the appropriate Path Selection Plugin (PSP) for your ESXi ?

Do not wait... check with your storage vendor. As a VMware administrator, In the past I'd my own reasons to choose Round Robin ahead of MRU and Fixed. But that may not be always good for the below reason.

Each storage vendor has their own method of handling I/O. For all recent Active/Active storage processors (SP), you will see two paths to a given LUN in VMware. But only one processor will actually own the LUN. The path to this storage processor is called as the Optimized path and the path to the other will be Unoptimized path. VMware PSP (MRU and Fixed) will always send its request to the Optimized path and once it reaches the SP, it will internally transfer the request to the other SP. In short ALUA is something which helps the array to service its I/O request using the interconnects between the SP.

In scenarios where the Optimized path fails, VMware vSphere PSP will choose the PSP and failback based on the PSP. I…

VMFS locking mechanisms | VMware

In a multi-host storage access environment like vSphere, a locking mechanism is required for datastore/LUN to ensure data integrity. For VMFS there are two types of locking mechanisms:
SCSI reservationsAtomic Test and Set - ATSSCSI reservations
This method is used by storage which does not support Hardware Acceleration. In this method, the host locks the datastore when it execute operations which requires metadata protection and will release the lock once it completes the activity. SCSI reservation does not lock a LUN, but it reserves the LUN to get the On-disk lock. Whenever a host locks, it must renew the lease on lock to indicate that it stills holds the lock and not crashed. When a new host need to access a file, it checks whether the lease has been renewed. If it hasn't renewed, another host can break the lock and access it. In a multi-host environment, excessive SCSI reservations might degrade the storage performance.
The operations that require reservation are : Creating, resign…

Virtual NUMA | The VMware story

NUMA - Non Uniform Memory Access
NUMA, a term which comes along with Symmetric Multi-Processing or SMP. In the traditional processor architecture, all memory access are done using the same shared memory bus. This works fine with small number of CPUs. But when the number of CPUs increase (after 8 or 12 CPUs), CPU competes for control over the shared bus and creates serious performance issues. 
NUMA was introduced to overcome this problem. In NUMA architecture, using advanced memory controller high speed buses will be used by nodes for processing. Nodes are basically a group of CPUs which owns its own memory and I/O much like an SMP. If a process runs in one node, the memory used from the same node is referred to Local Memory. In some scenarios, the node may not be able to cater needs of all its processes. At that time, the node makes use of memory from other nodes. This is referred to as Remote Memory. This process will be slow and the latency depends on the location of the remote memory…