Asked on Super User by Franck Dernoncourt, 9 months ago. No reply there for at least a week.
Why does the file transfer speed fluctuate wildly when copying files from an SD card to an SSD via a USB card reader?
I am copying 300+ GB of large files from an SD card to an internal SSD using a USB SD card reader, and the transfer speed fluctuates heavily. For example, it starts around 80–90 MB/s, then suddenly drops to a few MB/s, sometimes even below 1 MB/s, before jumping back up again. This cycle repeats throughout the transfer, but without any clear frequency and each cycle is rather different. Details: SD card: SAMSUNG EVO Select Micro SD-Memory-Card, 512GB microSDXC 130MB/s Full HD 4K UHD, UHS-I, U3, A2, V30. Card reader: SmartQ C307 USB 3.0 Portable Card Reader for SD, SDHC, SDXC, MicroSD, MicroSDH
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Why does the file transfer speed fluctuate wildly when copying files from an SD card to an SSD via a USB card reader?
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Question by Franck Dernoncourt on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.