[NTLK] flash longevity question
dan at dbdigitalweb.com
Wed Sep 21 13:46:09 PDT 2022
I have continued to dig into this topic wondering when the line happens between SLC (100,000 write cycles)/MLC (30,000 cycles)/TLC (3,000 cycles). It seems that up to 2GB is SLC and after that MLC. Although it could be SLC up to 16GB, but not likely. MLC is usually 16GB to 64GB with TLC anything over 64GB. Although I did find a few SD cards that were TLC and 32 or 64GB. This applies to USB thumb drives as well. And most of these devices do NOT have any user accessible data like SMART to tell you if it is using spare blocks and about to die. The usually just write-lock and you hope you can get the data off to another device.
A few vendors actually DO have programs or give the option to access the chips write-cycle data which is similar to SMART. Kingston, Swissbit, and ATP are three that do. But it is surprising that none of the top vendors such as Samsung or Sandisk offer this. One commercial tool I came across HDsentinel https://www.hdsentinel.com/how_to_monitor_sd_card_health_status.php will access several brands of cards that offer this feature. Most of the vendors offer a tool to download free of charge on their sites as well. And I am sure there are open source solutions out there. There are plenty of open source SMART tools or scanning tools. For example over at portableapps.com there is crystaldiskinfo (and the main site https://crystalmark.info/en/software/crystaldiskinfo/ as well) and https://hddscan.com/ while not open source is free and one of the better ones I have found for windows. Although I am not sure how effective these tools will be at detecting bad blocks. It depends on if the device hides this information substituting spare blocks to the scanner or not. In normal magnetic HD's it will show the bad blocks and where even if spares are used. And if you do use HDDScan on a flash device, only use simple READ mode or you will be using write cycles. Crystaldiskinfo may be able to pull some status data from a flash device, depending if they vendor has any open standards in use. But as I said, most do not.
I also saw Sandisk (Western Digital) now suggests powering cards/flash devices once a year.
While this is not directly applicable to our Newts, it does fit into the topic and I felt would be helpful to anyone using such higher capacity flash devices on the list (which I bet is everyone). :)
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