Ultra USB 3.0 Dual writing SLOWER THAN USB2.0

Hello there, i bought this flash drive (dual ultra 3.0 64GB) yesterday and i’m getting VERY SLOW writing speed.

At first, it starts writing like 50MB/s but after a few seconds the speed starts decreasing until it reaches 10MB/s. After that, it doesn’t get any faster, in fact, sometimes decreases until 6MB/s. It’s even slower than my 2.0 drives!

I’ve got a Lenovo Ideapad 310 with a i5 6200 2.3Ghz and 8GB RAM. Of course it’s plugged to a USB3.0 port and have all the drivers updated. 

I’ve just tried it on a 2.0 port and stays at 11MB/s, just like in the 3.0. Tried another 3.0 flash drive (verbatim 128GB) on the same 2.0 port and got 25MB/s (wich es good for a 2.0 port)

I’ve formated the flash to NTFS so i could transfer big files, but i think it shouldn’t cause any lost of speed, at least not to the poor 11MB/s i got

Anyways, sorry for bad english, and thanks to everyone that replies

exfat is a better choice than NTFS for removable drives. exFAT also supports large single files.

for the transfer speed issue you are seeing this is normal for the ultra line of USB drives from sandisk. The read speeds are high and defined in the specs but there is no write speed published. What you are seeing is normal for this product. if you are looking for high write speed drives you should look at sandisk extreme product line. 


I have the same problem… high speed at the beginning and after it is very slow (and sometimes à 0 kb/s for some seconds)

The problem arrive when i update my os from W10 1703 to W10 1709… few days ago.

Is there an issue from Sandisk or Microsoft to solve this problem ?


Is the drive still configured in Windows to be buffered?

I beg to differ.

This DUAL drive USB 3.0 is touted to perform up to 150MB/s not mb/s (mega BYTES not mega bits), on my system it should perform around 97MB/s write speed, read speed is approximately 135MB/s as the Sandisk Ultra Flair USB 3.0

It has been confirmed by Sandisk Global Customer Support that it is a device issue, they already know of slow Write speeds for some of the Flash drives.

This slow read issue also appy to other Sandisk USB 3.0 devices including the Extreme (27 MB/s_CrystalDiskMark) I have other high performance USB 3.0 drives similar to the Extreme and those write at  150MB/s-160MB/s.

It is NOT normal, it is a Windows compatibility issue mostly concerning Windows 10.

Lexar also had these compatibility issues with their Jump Drives, they found the solution and rolled out a Firmware this Year to address Windows compatibility (previously MASS STORAGE DEVICE under Device Manager needed to be uninstalled_Restart before it’s recognised)

The Lexar Jump Drive P20 writes at 160MB/s according to CrystalDiskMark 5.5, a 200MB file is near instant transfer, blink and its done.

I am using my two(2) SanDisk USB device for last 2 years. And, Both are working fine. 

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The drive does not support write cache… information given by Windows.