PowerShell using hashtable - powershell

Question

The below scripts works, but it takes a long time to complete the job. Can somebody help me to convert this script to faster way.
$servers = Get-Content Servers.txt
$TCount = $servers.Count
$count = 1
foreach ($server in $servers) {
Write-Host "$Count / $Tcount - $Server" -NoNewline
$Result = Get-VM -Name $server | Set-Annotation -CustomAttribute "SNAP" -Value "True"
if ($Result.Value -eq "true") {
Write-Host "`t - Success" -fore "green"
} else {
Write-Host "`t - Failed" -fore "Red"
}
$count = $Count +1
}

Answer 1

How is it possible for something like Get-HardDisk -VM "myVM" to work at all? After all, “myVM” is a string, not a VirtualMachine, so shouldn’t this fail?
The reason this works is because VI Toolkit takes advantage of a feature of PowerShell that lets you transform the arguments you receive on the command line. This is the basis of what we call the VI Toolkit’s “Object By Name” feature: If you specify a string where an object should be, VI Toolkit works behind the scenes to replace this string with the object that the string represents.
Inevitably this lookup has a cost, the question is how much is that cost? This brings us to a rather unfortunate property of VI Toolkit, which is that when you get a VM, all filtering is done on the client side. On one hand this is good because it allows us to support wildcards and case-insensitivity. However there is one very unfortunate consequence, which is that it takes just as long to load one VM as it takes to load all of them (more on how we are improving this below). This is the basic reason that the second example is so slow: every time Get-HardDisk is called, VI Toolkit looks up that one machine object behind the scenes.
http://blogs.vmware.com/PowerCLI/2009/03/why-is-my-code-so-slow.html
try:
$servers = Get-Content Servers.txt
$VMs = Get-VM | Where-Object {$_.Name -in $servers}
$TCount = $servers.Count
$count = 1
foreach ($vm in $VMs)
{
Write-Host "$Count / $Tcount - $Server" -NoNewline
$Result = $vm | Set-Annotation -CustomAttribute "SNAP" -Value "True"
if ($Result.Value -eq "true") {
Write-Host "`t - Success" -fore "green"
} else {
Write-Host "`t - Failed" -fore "Red"
}
$count = $Count +1
}
to load the VMs once, then loop over the $VMs to add the annotation.