Today I got an error while creating a Search Service Application for SharePoint 2013:

PS C:\> $SearchSA = New-SPEnterpriseSearchServiceApplication –Name “Enterprise Search Service Application” –ApplicationPool “Search App Pool” –DatabaseName “Search”

New-SPEnterpriseSearchServiceApplication : Value cannot be null.
Parameter name: indexLocation

To resolve this I just started the Search Service Instance on each (search) server in the farm and set it’s “DefaultIndexLocation” property.

After that I could create the Search Service App.

PS snippet:

"SearchServer1", "SearchServer2" | % {
    $svcInst = (Get-SPServer -Identity $_).serviceinstances | ? { $_.GetType().FullName -eq "Microsoft.Office.Server.Search.Administration.SearchServiceInstance" }
    $svcInst.DefaultIndexLocation = $defaultIndexLocation
    $svcInst.Update()
    $svcInst.Provision()
}

This did it.