Splits a large log file using PowerShell. Tested against very large multi-terabyte log files.

SplitLargeLogFile.ps1

 # Split Large Log File
$inputFile = "C:\temp\VeryLargeLogFile.log"
$outputDirectory = "C:\temp\logFileSplit"
$outputFileName = "LogFile"
$outputFileExtension = "log"
$upperBound = 500MB

New-Item -ItemType Directory -Force -Path $outputDirectory

$fromFile = [io.file]::OpenRead($inputFile)
$buff = new-object byte[] $upperBound
$count = $idx = 0
try {
    do {
        "Reading $upperBound"
        $count = $fromFile.Read($buff, 0, $buff.Length)
        if ($count -gt 0) {
            $to = "{0}\{1}.{2}.{3}" -f ($outputDirectory, $outputFileName, $idx, $ext)
            $toFile = [io.file]::OpenWrite($to)
            try {
                "Writing $count to $to"
                $tofile.Write($buff, 0, $count)
            } finally {
                $tofile.Close()
            }
        }
        $idx ++
    } while ($count -gt 0)
}
finally {
    $fromFile.Close()
}