PowerShell for Failover Clustering: Getting Started

PowerShell for Failover Clustering: Getting Started

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Hi Cluster Fans,

 

Amongst the long list of features that is being added in Windows Server R2, Clustering team is also providing a set of PowerShell cmdlets (“command-lets”) to manage your Failover Cluster.  Hopefully this is not news for most cluster administrators as we have publishing information on the blog and in our webcasts.  We have written a guide for using PowerShell in the Beta release and will add additional information shortly for the RC release:  PowerShell for Failover Clustering in Windows Server 2008 R2.

 

Cluster PowerShell cmdlets have come a long way from Beta to RC.  There have been quite a few changes in some of the cmdlets, cmdlet names and parameter names.  These changes have been made to improve stability, consistency among cmdlets and to ensure that they are self-discoverable.

 

 

Naming Convention

 

All Cluster cmdlets adhere to the naming convention guide line set by the PowerShell Team.  Every cmdlet can be broke in two parts, a verb and a noun.

 

While designing the names of these cmdlets, we took action oriented approach.  What I mean is, all our cmdlets corresponds to an action that can be performed on a cluster object.  This should give administrators a jump start with using clustering cmdlets to reduce the learning curve.

 

 

Verbs

 

Below is a table that lists all the verbs used by cluster cmdlets with an explanation.  The table does not detail the cmdlets.  The Idea is to help familiarize yourself with the verbs and that should help a user discover the right cmdlets for the operation.

 

Verb

Description

Add

The verb is self explanatory.   All the cmdlets that start with the verb Add would add the noun to the Cluster.  For example, Add-ClusterDisk, would add Disks to the cluster, Add-ClusterGroup would add a group to the cluster.

Block

We have only one cmdlet that has the Block verb and that is Block-ClusterAccess.  This cmdlet is used to manage user permissions and block would deny permissions on the cluster.

Clear

Cmdlets starting with Clear should help an administrator recover or re-claim a lost node or disk due to incomplete cleanup or information still lingering on them due to incomplete cleanup. 

Get

This should be the simplest and easily discoverable.  The Get-Cluster* cmdlets are to query either individual or all cluster object. For example, Get-ClusterNode is equivalent to Cluster.exe Node, Get-ClusterGroup is equivalent to Cluster.exe Group.

Grant

Cmdlets starting with Grant are among the set of cmdlets available to manage user permissions on Cluster.  This can be paired up with Block.

Move

If you need to perform a Move operation on a cluster object, you need to be looking at cmdlets that start with Move to update the location of a cluster resource or group.

New

There is only one cmdlet that start with New and that is New-Cluster used to create a cluster.

Remove

Cmdlets starting with Remove should help you delete\destroy a cluster object that you do not need.  For example, Remove-ClusterGroup, will delete a group.  Remove-Cluster should destroy the cluster.

Repair

We have a cmdlet Repair-ClusterShareVolume that would enable us to Run ChkDisk and Defrag on a CSV Volume.  This cmdlet needs to be run on a cluster node.

Resume

Any cluster object that can be suspended (paused) can be resumed using Resume-Cluster* cmdlets.

Set

This verb is not as obvious and a little harder to understand, but not really if you continue reading  :).

Set-Cluster* cmdlets were introduced to make some non-trivial tasks trivial, for example, setting values of cluster object parameter ( private properties), setting Group preferred owner list, or resource owner list.

Start

Cmdlets starting with Start are equivalent to Online or bringing a cluster resource up.  For example, Start-ClusterResource, Start-ClusterGroup, Start-Cluster, Start-ClusterNode.

Stop

Stop is equivalent to Offline.

Suspend

After knowing about Resume, you can guess that Suspend is used to pause a resource.

Test

Some interesting and more common cmdlets start with Test verb.  There are two cmdlets that start with Test, namely Test-Cluster (to run the “Validate a Configuration…” wizard) and Test-ClusterResourceFailover (to simulate a resource failure).

Update

Again two cmdlets start with Update.  We have Update-ClusterIPResource (used to renew\release the DHCP IP Address leases) and Update-ClusterVirtualMachineConfiguration (used to refresh a VM’s information after a change)

 

I understand that there is change in terminology and it could take a while for us to get used to it, but it is a necessary design decision to align with the changes in technology.

 

I would also agree that some of you that the selection of verbs is somewhat inconsistent with our UI, but this is to align with the larger Windows Server goal of consistent naming conventions, which gives us a limited set of verbs to use.

 

 

Nouns

 

Now let’s move on to the nouns…

 

The interesting part of the cmdlets is the noun, the second part of the cmdlet.  The first word is usually Cluster followed by a cluster object.  For example, resource is a cluster object, so the appropriate noun would be ClusterResource, group is a cluster object, so it's ClusterGroup.

 

We do have a smaller set of cmdlets that have only one word (as noun) and that is cluster. Some examples are New-Cluster, Get-Cluster.

 

With some knowledge of verbs and nouns, you should have some guidance towards discovering the cluster cmdlet you need.

 

 

Discovering Parameters

 

One of the objectives of PowerShell is self-discovery.  If you type '-' and press <tab> you should get the name of parameters which the cmdlet accepts.  If you press <tab> again you should get the next parameters.

 

Another way to learn about the cmdlet is to view the built-in help topic. I know as of today there is no MSDN documentation available for the cmdlets, but do you really need it?  Have you tried Get-Help on any of Cluster cmdlet?  If not, please try it and send us any feedback.  

 

This should not be new for any PowerShell user and don’t worry, I do not intend to talk about Get-Help and using <-><tab> in this section.

 

Some simple things first…

 

All our cmdlet's can be run from a cluster node or from a remote client.  The cmdlets ship as part of admin pack and works with PowerShell V2.

 

For these cmdlet's to work against a cluster, we do need to provide cluster name.  There are multiple ways to provide cluster information to a cmdlet.

 

1.       Every cmdlet has a -Cluster parameter, where you can specify the name of the cluster, or an IP address of the cluster, or the name of a Network Name resource type hosted on the cluster. If I am confusing you, sorry, but for now just keep in mind the -Cluster parameter.

2.       Most of our cmdlet do accept Cluster Object as piped in input.  And a cluster object can be obtained by using Get-Cluster -Name <Cluster Name>.  Get-Cluster is the only cmdlet that does not have a -Cluster parameter.

3.       If you are executing a command on a cluster node, -Cluster need not be specified.  The cmdlets are usually intelligent enough to detect that you are working on cluster node.  But if you are managing multiple clusters from a cluster node, please use the -Cluster parameter to address appropriate cluster, if not specified, the cmdlet would assume that you are working with the local cluster.

4.       The -Name parameter allows you to specify an object name representing the noun in the cmdlet.  For example, Get-ClusterResource -Name <resource name>.  If you provide a group name or any other name that is not a resource, the cmdlet would return an error.

5.       Positional parameters!  Positional parameters are parameter values that are not paired up with the parameter name.  The Idea behind positional parameters is that a user does not always type the parameter name, if the values can be identified based on position.  Most of our cmdlets are expected to work with positional parameters.  In most cases the value for -Name is positional parameter, but there are some cases where the noun can be passed in as a piped in object and in that cases the position shifts.

For example, you could do the below to move a group to node n1

Get-Clustergroup <group name> | Move-ClusterGroup n1

 

In the example above <group name> is taking the advantage of positional parameter as I have not linked the value with any parameter, but then Move-ClusterGroup accepts -name <group name> -node <destination node>. In the example above, the cmdlet is getting the group object through piped input, thus it assumes that the parameter passed to it is a node name.

 

The Idea here is to keep things simple and make them work in most obvious cases.

 

 

Cluster.exe to PowerShell Comparison

 

To help you get started with the cmdlets, I built this table which shows some common cluster.exe command and their matching PowerShell cmdlets.

 

Cluster.Exe Command

PowerShell Command

Cluster.exe <Cluster Name> /prop

Get-Cluster <Cluster Name> | fl *

Cluster.exe <Cluster Name> /priv

Get-Cluster <Cluster Name> | Get-ClusterParameter

Cluster.exe <Cluster Name> group

Get-ClusterGroup -Cluster <Cluster Name>

Cluster.exe <cluster Name> node

Get-ClusterNode -Cluster <Cluster Name>

Cluster.exe <cluster name> res

Get-ClusterResource -Cluster <Cluster name>

Cluster.exe <Cluster name> net

Get-ClusterNetwork -Cluster <cluster name>

Cluster.exe <cluster name> netint

Get-ClusterNetworkInterface -Cluster <cluster name>

Cluster.exe <cluster name> group /move:<Node  name>

Move-ClusterGroup -Name <group name> -Node <Node name> -Cluster  <cluster name>

Cluster.exe log

Get-ClusterLog

Cluster.exe <cluster name> /create …

New-Cluster

Cluster.exe <cluster name> group /add

Add-ClusterGroup

Cluster.exe <cluster name> group <group name> /on

Start-ClusterGroup -Name <group name> -Cluster <cluster name>

 

 

That is all for now, please check back later for more PowerShell information.

 

Thanks,

Vikas Kumar

Software Development Engineer in Test

Clustering & High-Availability

Microsoft

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