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Q: I outgrew my old flash drive, so I bought a larger one and moved all my files to it.  I thought I would just erase the old one and use it as a sneakernet.  As I was deleting all the files, I kept getting prompted “Are you sure?” so I finally just decided to format it and be done with it.  The system then asked me if I wanted to do a regular format, or a “quick” format.  I’ve been doing this for years, and never really thought about it before, but exactly what is the difference? 

– John M.
Fort Walton Beach, Fla

A: Ah, a good old-fashioned basic question for a change!  How refreshing.  Okay, John, before I give you your answer, let me fill-in the background for those of my readers who perhaps are not as geeky as you are.

A format of a storage medium is the process of preparing it to store data.  Typically, this entails writing operating system information into the first few sectors of the drive, creating the directory structure, which, on an empty disk consists simply of the root directory, but this is needed before any other directories can be created.  The format operation then proceeds to write data to every single sector on the drive.  Any areas that fail are marked as bad. 

It is that last operation – writing data to the entire drive – that causes a format operation to take so long.  Enter the “Quick Format”.  A quick format does everything a full format does, except write data to every sector.

Now, there are some subtleties that you should be aware of.  Not writing to every sector may save time, but it does leave the contents of the old file data in tact on the drive.  In normal use, that probably will not be a problem.  Using normal access techniques, the drive will appear empty.  But if you had any sensitive files on the device, such as financial data, medical information, password lists, etc., these files could be recovered by someone who knows what they are doing in the event your device is lost or stolen.  Doing a full format doesn’t necessarily guarantee unrecoverability, but it is a far sight more secure than doing nothing at all.

So, it sounds like you should always perform the lengthy format operation then, right?  Well, not necessarily, and especially when dealing with flash devices.  Most, if not all flash devices are rated for a limited number of read and write cycles.  A full format operation writes to every single sector of the device, so should be used sparingly.  Remember, memory chips in cameras, smart phones, and MP3 players are all flash-based, so this goes for them too!  As with most things related to computers, it is up to you to find the personal balance that works best for you and your particular hardware.