They do, but not quite in such a simplistic way.  Basically, there&#x27;s one service that manages the individual drives, and then another service (Colossus) that sits on top of it and provides the abstraction of an infinite, highly-available, perfectly robust filesystem.  So services like YouTube just specify a path, data, an owner, and a replication policy and then hand it off to Colossus to find free space on one of the zillions of disks.  There&#x27;s a side mechanism for quota &amp; budgeting.<p>It&#x27;s unclear from the article whether YouTube&#x27;s 1P&#x2F;day is pre-replication or post-replication.  I&#x27;d just assumed post-replication; it doesn&#x27;t really change the conclusion in a material way.  (Rather than the answer being &quot;1 person&quot;, it becomes &quot;2-3 people&quot;.)<p>And yes, you do need 2x (or more commonly, 3x) the disk space.  You can use error-correcting codes to correct single-bit errors (Colossus uses Reed-Solomon), but that won&#x27;t help you if there&#x27;s a fiber cut and a whole datacenter goes offline.