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It has been said that continuous writing on an SD card can cause wear and tear on the memory cells, which can eventually lead to the failure of the card. One of the answer to my question here How to achieve SD card's life service to 10 years or more? said that flash memories have limited amount of write cycles (10k to 100k average). If given a scenario were an SD card has 64GB capacity and it consumed only 5GB of written data, do you think it will soon experience wear and tear or perhaps failure if this 5GB used space reached the 100K write cycle eventhough there is still ample amount of unused space?

Hashim Aziz
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ordinary_guy
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1 Answers1

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Good information is to be found in the post Quick reminder that SD cards with wear-leveling are now fairly common (i.e. WD Purple microSD) from 2019:

Vast majority of SD cards do not have wear-leveling, and might keep on writing to the same blocks over and over. In the end you wear out the card, and it becomes defective.

SD cards with wear-leveling used to be expensive, and small in size, and were usually reserved for specialized use (i.e. industrial applications). Today, you can get a 64GB SD card with WL for as low as 15 EUR.

Keep in mind that even though the manufacturer of the SD card might use terms such as "high endurance" on their product, you have no guarantee the card actually employs wear-leveling. Unless it's specifically stated in the specs, it's safe to assume a "high endurance" card will not have wear-leveling.

The author got this statement from WD Engineering regarding his wear leveling inquiry:

Our WD Purple MicroSD's do both static and dynamic wear-leveling. Meaning all blocks across whole address space are considered for wear leveling regardless of if and how the blocks are used. This keeps the number of program erase cycles consistent on all blocks.

The answer is then that if a portion of the card is used again and again, its failure means the failure of the card. You should look for cards that support wear-leveling, in order to distribute the load over the entire card (although finding this spec might not be easy).

harrymc
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