Author Posts

August 14, 2018 at 7:51 am

Hi,

New to the forums and new to powershell remoting.

I have a script that traverses a local folder and filters for a specific filename pattern and deletes the files.

Get-ChildItem -Path c:\users -Filter "*.auc" -Recurse -ErrorAction SilentlyContinue -Force | Remove-Item -Force

Everything works like a charm, when running on a local machine.

I want to run this script across several machines, but what takes 2-5 seconds when running local, takes 1-2 minutes when running it remote.

I can guess that the Get-ChildItem is returning all the objects back over the network and into the calling console and that is what makes an impact on the performance.

I understand that I could start some background jobs and have them running in parallel and just check when they are done.

But what I really would like to know and understand, is whether there is a way to just execute a script on a remote machine? An old school fire and forget, but with the local execution performance. I could easily push the same script onto the servers, in the same location and then execute it.

Is it possible to execute a local stored script via powershell remoting, but make sure that the execution is actually done local? Should I start a powershell.exe with parameters to achieve the results expected?

Any other ideas to achieve what I'm looking would be of incredible help!

August 14, 2018 at 1:32 pm

So, you don't mention how you've run this remotely. I suspect you're using a UNC or a mapped drive.

Were you to use Invoke-Command to send that exact command (referencing a drive letter that it local to the remote machine) over the network, it *does* execute locally. Now, the Remoting provider process is a background process, so it definitely can be given less priority than an interactive process; as an admin, you can obviously modify process priority. But it would definitely execute locally, without doing the multiple round-trips your current command is doing.

August 16, 2018 at 7:20 pm

So if we were to use the Invoke-command but referencing the a script that is locally stored on the host of the console, will it take the entire content of the script, go to the remote computer and then execute it locally and only bring back the results? Am I understanding this correctly?

August 16, 2018 at 7:37 pm

Hello Mr. Jones, I just finished reading your book "PowerShell in a month of lunches" and I first and foremost have to thank you for co-authoring such a wonderful book. And because of this book, instead of googling scripts, I was able to write my scripts from scratch. So a big thanks to you and  Mr. Hicks!!

So after reading the chapter 13 of the book, which explains the benefits of using the Invoke-Command, I incorporated it in my script instead of just using the plain SMO for querying SQL Server. But I have noticed that when I explicitly write the entire code in the -ScriptBlock, the Invoke-Command returns the results in 5-8 seconds, but if I use the Invoke-Command with -Filepath, the same query takes on a average 25-35 seconds longer? I am querying the same SQL Server over WAN from the same console.
Also, in general, does parameterization of a script degrades its performance?
Below is the code for your reference;

Fast results: 5-8 seconds

Invoke-Command -ComputerName SERVER -ScriptBlock {[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.SMO") | Out-Null
 $server = New-Object Microsoft.SqlServer.Management.Smo.Server "SERVER"
 $server.Databases |
 Select @{label="Server";Expression={$_.Parent.name}},
 @{Label="DB_ID";Expression={$_.ID}},
 @{label="Database Name";Expression={$_.Name}},
 Status,
 IsAccessible,
 UserAccess,
 LogReuseWaitStatus,
 @{label="Size_MB";Expression={$_.Size}},
 RecoveryModel,
 AutoShrink,
 AutoClose,
 CompatibilityLevel,
 Owner | Sort-Object DB_ID |Format-Table * -AutoSize}

And here is with the FilePath parameter : Slow results on an avg 25-40 seconds slower.

Invoke-Command -FilePath "C:\Users\MS\Documents\WindowsPowerShell\Scripts\Invoke_cmd_bkup.ps1" -ComputerName SERVER

 

August 16, 2018 at 7:58 pm

There's a bit more overhead using -FilePath because PowerShell has to open the local file, package it, and transmit it, before the remote end can start executing. It's usually pretty minimal in my own experience; I've not run into a 3x penalty like you're seeing. If I was hell-bent on figuring out where the difference was, I'd probably run some very detailed traces with Trace-Command to see if there's a particular part of the process that's taking notably longer.

August 16, 2018 at 8:39 pm

I'll give that Trace-Command a shot to figure out because these are simple scripts querying SQL Server to get basic info and if it takes 40-45 seconds, it's a deterrent for my colleagues to use as they are all BASH guys and I want to make PowerShell work and look good 😉

Also, my other question was about variables. I have also noticed that when scripted using variable, there was a 2x-2.5x penalty? Is that some that is expected?

August 16, 2018 at 11:33 pm

Mr. Jones, I ran the Trace-Command

Trace-Command -Name ParameterBinding -Expression {Invoke-Command -FilePath "C:\Users\MSA050415\Documents\WindowsPowerShell\Scripts\Invoke_cmd_bkup.ps1" -ComputerName SERVER} -PSHost

and the output below really didn't help me. Am I using the right tracesource? What should I be doing instead if this is not sufficient?

 DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Invoke-Command]
DEBUG: ParameterBinding Information: 0 :     BIND arg [C:\Users\MSA050415\Documents\WindowsPowerShell\Scripts\Invoke_cmd_bkup.ps1] to parameter [FilePath]
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.String]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         Executing VALIDATION metadata: [System.Management.Automation.ValidateNotNullAttribute]
DEBUG: ParameterBinding Information: 0 :         BIND arg [C:\Users\MSA050415\Documents\WindowsPowerShell\Scripts\Invoke_cmd_bkup.ps1] to param [FilePath] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 :     BIND arg [SERVER] to parameter [ComputerName]
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.String[]]
DEBUG: ParameterBinding Information: 0 :             Trying to convert argument value from System.String to System.String[]
DEBUG: ParameterBinding Information: 0 :             ENCODING arg into collection
DEBUG: ParameterBinding Information: 0 :             Binding collection parameter ComputerName: argument type [String], parameter type [System.String[]], collection type Array, element type [System.String],
coerceElementType
DEBUG: ParameterBinding Information: 0 :             Creating array with element type [System.String] and 1 elements
DEBUG: ParameterBinding Information: 0 :             Argument type String is not IList, treating this as scalar
DEBUG: ParameterBinding Information: 0 :             COERCE arg to [System.String]
DEBUG: ParameterBinding Information: 0 :                 Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :             Adding scalar element of type String to array position 0
DEBUG: ParameterBinding Information: 0 :         Executing VALIDATION metadata: [System.Management.Automation.ValidateNotNullOrEmptyAttribute]
DEBUG: ParameterBinding Information: 0 :         BIND arg [System.String[]] to param [ComputerName] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Invoke-Command]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Invoke-Command]
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing