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VmWare Certified Professional – Advantages of Getting a VCP Certification

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There has been a quiet revolution in computers over the past couple of years, but only developers and IT professionals are aware of it. This revolution involves the new found popularity of virtual machines. While different types of virtual machines have been around for decades, they are now more popular than ever. People have figured out clever uses for using virtual machines in everyday settings. If you are scared to open a file because you think that it might be a piece of malware, then you can just open it, in a vm image and let the damage happen in there. Also you can use the power of virtual machines, to make your computing sessions portable. You can easily make an image of your hard drive, and use it on any system that has a vm player installed. Also, virtual machines are extensively used in Enterprise I.T infrastructures, with the advantage being that a single hardware machine can host several virtual servers. The leader in this field right now is of course VmWare.

VmWare has been a leader in making the software that creates and manages virtual machines, accessible to the average user. Since there are a lot of companies starting to use vm images as server solutions, there is a new market that has opened up. There is also a drought of people that can fulfill the needs of this market. The market is for people that know how to operate the VM software and set it up for a large amount of customers. This is where becoming a VmWare Certified Professional can come in handy. A VCP Certification will tell your potential employer that you know everything about virtualization and can deploy it on their enterprise machines. To become a VCP3 certified you must take the VCP-310 Exam or the newest VCP-411 Exam in order to get the VCP4 certification. Training on VmWare VSphere can also be very helpful for learning the exam requirements of VCP Certification and finally passing the exam.

Most people that get a certification in the IT profession will know how to handle servers in an enterprise setting. What they will have a problem with though, is trying to set up an enterprise server in a virtual setting. There are special needs and precautions that one must take when they are deploying servers in this manner. A virtual server set up, can be a delicate eco system, which one must be careful. Becoming a VmWare Certified professional will show that you know how to do this. You will receive all of the proper training that you need to be able to accomplish the task. You will also be able to physically display the VCP logo, on your web site or business cards. This brings an extra level of professionalism while you are stating your case to your employer.

Becoming someone who is a VmWare Certified Professional will help you in the long run with your employment goals. Virtual Machines are popular in the present and they will be even more so in the future. Show your new boss that you are already one step ahead
Source by Harris Andrea

Storage Plugins – SATP, PSP

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This article is Part of Becoming a VMware Storage Expert series

This is the second part of Storage Plugin to understand the whole picture please check this post. This article will go through how SATP and PSP work with Pluggable Storage Architecture(PSA).

SATP – Storage Array Type Plugin

Storage Array Type Plug-ins (SATPs) are responsible for array-specific operations. The SATPs are submodules of the VMware NMP.

ESXi offers an SATP for every type of array that VMware supports. ESXi also provides default SATPs that support non-specific active-active, active-passive, ALUA, and local devices.

Each SATP accommodates special characteristics of a certain class of storage arrays. The SATP can perform the array-specific operations required to detect path state and to activate an inactive path. As a result, the NMP module itself can work with multiple storage arrays without having to be aware of the storage device specifics.

Generally, the NMP determines which SATP to use for a specific storage device and associates the SATP with the physical paths for that storage device. The SATP implements the tasks that include the following:

  • Monitors the health of each physical path.
  • Reports changes in the state of each physical path.
  • Performs array-specific actions necessary for storage fail-over. For example, for active-passive devices, it can activate passive paths.

ESXi includes several generic SATP modules for storage arrays.VMW_SATP_LOCALSATP for local direct-attached devices.As of vSphere 6.5 Update 2 release, VMW_SATP_LOCAL provides multipathing support for the local devices, except the devices in 4K native format. To claim multiple paths to the local devices, you are no longer required to use other SATPs as you were in the earlier vSphere releases.VMW_SATP_LOCAL supports the VMW_PSP_MRU and VMW_PSP_FIXED path selection plug-ins, but does not support VMW_PSP_RR.VMW_SATP_DEFAULT_AAGeneric SATP for active-active arrays.VMW_SATP_DEFAULT_APGeneric SATP for active-passive arrays.VMW_SATP_ALUASATP for ALUA-compliant arrays.

PSP – Path Selection Policy

The plug-ins are submodules of the VMware NMP. The NMP assigns a default PSP for each logical device based on the device type. You can override the default PSP. For more information, see Change the Path Selection Policy.

Each PSP enables and enforces a corresponding path selection policy.VMW_PSP_MRU – Most Recently Used (VMware)The Most Recently Used (VMware) policy is enforced by VMW_PSP_MRU. It selects the first working path discovered at system boot time. When the path becomes unavailable, the host selects an alternative path. The host does not revert to the original path when that path becomes available. The Most Recently Used policy does not use the preferred path setting. This policy is default for most active-passive storage devices.The VMW_PSP_MRU supports path ranking. To set ranks to individual paths, use the esxcli storage nmp psp generic pathconfig set command. For details, see the VMware knowledge base article at http://kb.vmware.com/kb/2003468 and the vSphere Command-Line Interface

Reference documentation.VMW_PSP_FIXED – Fixed (VMware)This Fixed (VMware) policy is implemented by VMW_PSP_FIXED. The policy uses the designated preferred path. If the preferred path is not assigned, the policy selects the first working path discovered at system boot time. If the preferred path becomes unavailable, the host selects an alternative available path. The host returns to the previously defined preferred path when it becomes available again.Fixed is the default policy for most active-active storage devices.VMW_PSP_RR – Round Robin (VMware)VMW_PSP_RR enables the Round Robin (VMware) policy.

Round Robin is the default policy for many arrays. It uses an automatic path selection algorithm rotating through the configured paths.Both active-active and active-passive arrays use the policy to implement load balancing across paths for different LUNs. With active-passive arrays, the policy uses active paths. With active-active arrays, the policy uses available paths.The latency mechanism that is activated for the policy by default makes it more adaptive. To achieve better load balancing results, the mechanism dynamically selects an optimal path by considering the following path characteristics:

  • I/O bandwidth
  • Path latency

To change the default parameters for the adaptive latency Round Robin policy or to disable the latency mechanism, see the Change Default Parameters for Latency Round Robin.To set other configurable parameters for VMW_PSP_RR, use the esxcli storage nmp psp roundrobin command. For details, see the vSphere Command-Line Interface Reference documentation.

MPP – Multi Pathing Plugin

MPPs that are not implemented as SATPs or PSPs can be implemented as MPPs instead. MPPs run side by side with NMP. An example of that is EMC PowerPath/VE. It is certified with vSphere 4.x and is planned for vSphere 5.

Reference: https://docs.vmware.com/en/VMware-vSphere/6.7/com.vmware.vsphere.storage.doc/GUID-DB5BC795-E4D9-4350-9C5D-12BB3C0E6D99.html

What is Alua? How it works?

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This article is Part of Becoming a VMware Storage Expert series

ALUA stands for “Asymmetric Logical Unit Access”, as per t10 SCSI-3 specifications (www.t10.org/cgi-bin/ac.pl?t=f&f=spc3r23.pdf). ALUA occurs when the access characteristics of one port may differ from those of another port. In English this means the LUN could be seen via both storage processors as an active but only one of them owns the Lun. Hence there will be optimized and unoptimized paths, the I/O is allowed to the LUN.

But the performance of the owner Storage Processor is better than that of the non-owner Storage Processor. To allow the initiators to identify which targets would provide the best I/O, the ports on each Storage Processor are grouped together into target port groups. Each target port group is given a distinctive “state” (asymmetric access state [AAS]), that denotes the optimization of ports on one SP compared to ports on the other SP (for example, active-optimized versus active-non-optimized).

Target Port Groups

A target port group is defined as a set of target ports that are in the same target port asymmetric access state at all times. A target port group asymmetric access state is defined as the target port asymmetric access state common to the set of target ports in a target port group. The grouping of target ports is vendor specific.

Target port Group Support

Target port Group Support provides a method for determining the access characteristics of a path to a LUN through a target port. Target Port Group Support is often used with arrays that handle load balancing and failover within the Storage Processors. Target Port Groups allows path grouping. Each port in the same Target Port Group has the same port state, which can be one of the following state:
Active/Optimized
Active/Non-optimized
Standby
Unavailable
In-Transition.

Some storage arrays might not support some of the latter three states.


Reference from Mostafa Khalil
Alua Storage Array

Asymmetric Access State(AAS)

Ports in an ALUA TPG can be in the same AAS at all times with respect to a given LUN. TPG’s AAS are reported to the initiators in response to the REPORT TPGS command. The TPG descriptor is reported in byte 1 of that response.

Possible states are as follows:

  • Active-optimized (AO)—Ports are on the owner SP and provided the best I/O to the LUN.
  • Active-non-optimized (ANO)—Ports are on the non-owner SP. I/O to the LUN is less optimal compared to AO AAS.

ESXi 6 sends the I/O to TPGs that are in AO AAS, but if they are not available, I/O is sent to TPGs that are in ANO AAS. If the storage array receives sustained I/O on TPGs that are in ANO AAS, the array transitions the TPG’s state to AO AAS. Who makes that change depends on the ALUA management mode of the storage array

-Venkatesh Sekar