Extreme Pro 256GB Flash Drive - Write Speed drops dramatically after just several months multiple times

I bought a brand new SanDisk Extreme Pro 256GB USB 3.1 flash drive in 2018, and only used it for couple of months, the write speed dropped dramatically, from 350 MB/s to 20 MB/s. So I sent it to WD and got a replacement under the lifetime warranty. However, the brand new replacement had the same problem, and after several months its write speed dropped to 20 MB/s again. So, I asked for another replacement once more. This time, the replacement kept the high write speed of around 300 MB/s for almost two years, and all the sudden, it dropped to only 60-80 MB/s again, and I have to send it back for yet another replacement. I really don’t understand how these USB drives could be so unstable, and drop off the write speed so easily. The problem is that none of the three drives I have had, no matter it’s an original purchase or a replacement, all have the same write speed issues.

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Two years use supersedes “all of a sudden”. Name me something you have used that has lasted forever with no deterioration. Things wear out, especially things used a lot.

With your USB drive try defragging it. Try reformatting it, exFAT not NTFS. Try deleting the partition on it and starting from scratch with it. Windows’ diskpart works for starting over.

> diskpart * Run Command Prompt with Admin Rights.

> list disk

>…

> select disk 1 * Note: disk nbr is the nbr of the USB disk

> clean

> exit

Same issue here so now working with warranty support. Writes used to be straight line fast, around 350 MB/s, now looks like a roller coaster with single large files. I benched mine, when new, two years ago. So diskpart, and normal formatting does nothing! Only the SLOW format option, fast not checked, under Win 11 restores somewhat. Faster but still a roller coaster with speeds. My before and after fail with ATTO shows the story many other are seeing.

Last post, ever! Support did get back, thank you. However having to jump thru hoops and testing a second USB stick, also bad on the write speed, I moved on to and Nvme and external case. $45 total small and way faster. The second Extreme USB did have updated firmware…it is no longer reported bad with Diskinfo64. (rolls eyes) Good luck Scandisk.