Why is the file uploading to the server slow?

Question

PHP

Good afternoon, there is a bunch of nginx + apache + php
There is a script that accepts a file via

$f = fopen($dir.$filename, 'ab');
  fwrite($f, file_get_contents('php://input'));
  fclose($f);

So when you upload a file to the server, the speed drops to 70kb per second. FTP download is fast. Channel 100Mbit / s
Disabled nginx - the same result.
When transferring the script to another server - no problem. So there is a limit somewhere.
What could it be? There is no fine tuning of the server.

Answer 1

check memory_limit in php on both servers