Marketing over technical details, refuse to disclose what wear-leveling algorithm being used in specific product. That is what I heard from various community.

It is a little disappointed to me that while SD card is the only reasonably priced, compact, card-sized, user removable flash storage solution available in market, although technically possible, it seems that SDA and the manufacturers are not willing to support flash storage requirement of traditional operating system installation at all.

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Do not use SD card for operating system main stroage (like Pi).

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To purchase a discard-capable card for my application, I attempted to search on Web for SD 5.1/6.0 compliant cards and failed, then I searched for A1/A2 instead, then I came across this blog post...

So, after all, for these different SD card "classes", it's all about marketing instead of the actual performance...

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Given the fact that Raspberry is rather popular these days, and it utilizes SD card as system main storage, we can see that people on Internet complain about their SD cards bricked into a read-only state because of NAND wear-out.

Using SD card as system main storage, like what Raspberry does, will also invalid product warranty. We read from website of major SD card manufacturer like Samsung, in their warranty policy that a SD card will lose its warranty once it is used as system main storage.

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Discard operation in SD specifications is first disclosed to mass in 6.0 PLS, and according to a WDC Linux developer it was first available in 5.1 (full) spec.

In 6.0 PLS, it is advised not to apply discard operation to filesystem blocks (e.g. use of fstrim or discard mount option on Linux), which means, it should be used only for contiguous large block space (i.e. blkdiscard on Linux).

So by spec, SD card is clearly not suitable for scenario like Raspberry.

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It has been more than three years since the announcement of SD 6.0 specification, a wired thing is that I cannot even find a USB card reader in market that claim to support host-managed discard operation, which is a very basic requirement for installing operating system on modern NAND flash storage like eMMC.

Mastodon @ SDF

"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko