Does Erasing Flash Memory Shorten It’s Life?

Yes. Performing an Erase or “full format” shortens the life of the device. The erase function is also very slow.

Here are some additional questions based on the answer above which we will address in today’s post:

Is “erase” and “format” the same thing?

Erasing flash memory (a.k.a. Setting all bits to 0, also called a “full format” by Windows) does more damage. Flash memory has a limited number of times that it can be written, and the more you write to it, the more it degrades. With an erase function, you’re writing to the entire device.

With a format, all that’s happening is changing a few bits at the front of the device to say the rest of the memory space on the flash drive is available to be overwritten. This saves the life of the flash memory because the old data is not being overwritten, just flagged to do it at a later time.

Why would you need to erase a drive?

Since a format is changing just a few bits at the front of the device, it means all the data is still on the drive. The few bits we are talking about which are changed, is related to the file allocation table. The changed bits in the file allocation table, mean there are no longer instructions about the location of the digital files. Recovery software can scan the memory space and retrieve those files even though the file allocation table isn’t giving instructions on where they are located.

Think of the file allocation table as the table of contents of a book. If you tear out the table of contents of a book, but all the pages of the story are still there, it’s the same concept as formatting a device. Sure you can scan the pages to find chapter 12 with the part about Paul getting a bucket of water, it’s just hard. Same thing with formatting a drive, you can use recovery scanning software to find the files, but it’s hard. Coming back to the original question, why would someone want to erase a USB flash drive? One possible reason could be a security risk of some kind and the operator wants to insure no data is on the drive. For example, you are donating a flash drive and you had financial or medical records on the drive. By performing an erase, that data cannot be recovered.

Why does an erase take longer?

This is a bit more technical, so we will do our best to summarize. NAND memory is made of up silicon. The silicon die is then made up of planes, blocks and pages. The page is the smallest bit of silicon which can be programmed, but the block (which holds pages) is the smallest bit which can be erased or cleared. When you perform erase or full format, what you are doing is telling each block to drill down and erase each page. This takes time. When you format or even delete a file, the binary data is not going away, only the address on how to locate _that_ data is being taken away. Said another way, going back to my table of contents example, suppose someone asked you to tear out chapter 12, and they requested each page to be torn out individually. That is a lot slower than tearing out 5 or 10 pages at a time.

Why does an erase function shorten the life of the device?

If we think about my comment on formatting verse erasing, this question is fairly easy to answer. Since a format function doesn’t really change any of the data, only small bits of the file allocation table there isn’t much wear and tear. However, since an erase function performs a task to each block of the memory wafer, there is more wear and tear. Silicon is relatively sensitive material and will not last forever, therefore when more action is taking to the silicon the shorter the life cycle. Remember the comment made about a “page” being the smallest part of silicon which can be programmed? Well the “program” part is really making the silicon a positive or negative charge. Positive and negative charges are physical binary representations of zeros and ones. If we zero out the page with an erase function, over time, the silicon cannot hold a positive charge to denote the binary, and once the silicon cannot reliably hold a charge, the block is mapped out of usable memory (goes bad) and is no longer accessible.

As once can see, an erase function is not required unless you have a specific situation which requires it. Since the erase function is slower and shorts the life of the device, probably best not to use it, unless necessary.

Sourge: (English) Reference: Flash Trans Layer wiki.

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Rich Gates

Administator for started in 2004 with the concept of providing USB information for everything USB related. At the time, USB was gaining momentum and every day new products, articles and news became published. Today, the site is focused on bringing technical information, tricks and hacks to USB related products. The site does publish off topic information as well, to keep the variety up. Please visit the footer area of any page if you or your company is interested in article or product placement via purchased advertising.

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