What’s fog?
Fog, is a cloud that’s touching the ground.
And when it comes to cloud storage you can find yourself standing in thick fog were you to investigate where exactly in the cloud your files are stored.
You can download as many copies of a file as you want but if your public cloud storage provider tells you it’s keeping three or multiple copies of your file in it’s storage system how can you tell that they’re not all sitting on the same devices in the same server? Or in the same rack? Or the same data centre?
How can you tell that they’re in different countries or across continents if that’s what you’re paying for and how vulnerable are you to failures?
How to Tell if Your Cloud Files Are Vulnerable to Drive Crashes
This paper presents a new challenge—verifying that a remote server is storing a file in a fault-tolerant manner, i.e., such that it can survive hard-drive failures. We describe an approach called the Remote Fault-Tolerance Tester (RFTT). The key technique in an RFTT is to measure the time taken for a server to respond to a read request for a collection of file blocks. The larger the number of hard drives across which a file is distributed, the faster the read request response. Erasure codes also play an important role in our solution. We describe a theoretical framework for RFTTs and show experimentally that RFTTs can work in practice.
