As for the number of executions you have two choices:

1) Loop through adding multiple inserts to a single command.

$isFirst = $true

$commandText = "INSERT DiskSpace"

$wmiObject = Get-WmiObject Win32_LogicalDisk -computer 'SomeComputerName'

Foreach ($logicalDisk in $wmiObject)

{

if($isFirst) { $isFirst = $false } else { $commandText += "," }

$commandText += " VALUES ('" + $logicalDisk["DeviceID"] + "')"

}

$command = $conn.CreateCommand()

$command.CommandText = $commandText

$command.ExecuteNonQuery()

2) Loop through executing multiple commands.

$wmiObject = Get-WmiObject Win32_LogicalDisk -computer 'SomeComputerName'

Foreach ($logicalDisk in $wmiObject)

{

$commandText = "INSERT DiskSpace VALUES ('" + $logicalDisk["DeviceID"] + "')"

$command = $conn.CreateCommand()

$command.CommandText = $commandText

$command.ExecuteNonQuery()

}