Sandisk Extreme Pro USB 512Gb and 1Tb poor write speeds !?

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Having write speed issues with my old Sandisk Extreme Pro 512Gb and brand new 1Tb keys !. Write speed initially around 200Mb/s but quickly drops to 80-100 Mb/s after a three seconds which is unnaceptable. Tried NTFS (4k alloc) and ExFAT (256K alloc) formats to no avail, rebooted PC etc (Windows10). Using a high end Intel PC with fast USB3 ‘SS-10’ port. Source file on a VERY fast M2 drive (around 5Tb/s). Changing drive policy from ‘quick removal’ to ‘better performance’ gives the expected speed boost but only for a few seconds before dropping again to around 80-100Mb/s. Yes latest drivers and Windows updates applied.

What’s happening here Sandisk ?

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Your Windows security apps are validating every byte being written to ensure you’re not creating a flash drive to share that is infected with malware.

And never, NEVER, use a journalling drive format on a flash drive. Extra writes, slower speed, reduced drive life span. And yes I’m referring to NTFS. Use FAT32 or exFAT only.