Posts: 1
Registered: ‎02-26-2019

Ultra Flair 64GB USB 3.0 very slow write speeds

Hello, I just bought an Sandisk Ultra Flair usb 3.0 drive, the 64gb version. The write speeds to the drive are EXTREMELY slow for a USB 3.0 drive. I plugged it into a USB 3.0 port and copying about ~18gb of files to it, first of all it started at about 30 MBps instead of 60MBps and after transferring some files the speed dropped down significantly to an average of about 10 MBps, which is much slower than any of my other brand USB 2.0 drives. Both large files and small files transfer very slowly. I also have a Sandisk Ultra 256GB USB 3.0 drive and that one as well is slower than my other brand USB 2.0 drives. If this is intended operation I am very disappointed in Sandisk's false advertising "15 times faster than USB 2.0" which this drive was advertised as. Are there any fixes which can make the write speeds faster?

usb drive transfer.PNG
SanDisk Guru
Posts: 2,714
Registered: ‎07-23-2010

Re: Ultra Flair 64GB USB 3.0 very slow write speeds

Are you using it on the same machine as before?  Are you running the same OS as before?  Are you running the same AV as before?  And the same malware apps as before?  Is the OS downloading updates as you write to the USB drive?  These things impact speed also.  SanDisk's stats are on a machine doing nothing other than reading and writing to the USB drive.


Try running your machine in safe mode and see if the speed improves.

Important files = Backed up files
Posts: 1
Registered: ‎03-13-2019

Re: Ultra Flair 64GB USB 3.0 very slow write speeds

I have an Ultra Flair 128GB that does the same thing, except if ran even longer (before it locks up), as it runs it gets slow and slower, it dips down to about 6MB/s when there is a high # of writes, but sustained writing of larger files does average about 8MB to 10MB/s.


-  The OS is not updating.  That is disabled and done manually.

-  AV enabled or disabled makes no difference

-  Malware apps not running but system scanned and confirmed clean

-  Same behavior on rear port, front port, USB hub, and different system


In all cases removing the Ultra Flair and using a Sandisk Extreme USB3 instead, works fine without this slowdown.


It is slowing down as it gets hot and if left running hot it eventually locks up and can't be accessed until removed, allowed to cool, then plugged back in.   The only time it can achieve over 12MB/s is if it was sitting unused, then plugged in and a copy started before it warms up, and then only until it warms up, a minute or two at most.


I never expected 15 times faster than USB2 for writes, but I did expect it to be faster continuous writes than my 8+ year old USB2 flash drives which have dozens of times as many writes to them already.


This was all observed using the factory format.  At one point I had nearly filled it and wanted reuse it for something else and found it was impossible to delete all the files in a timely manner because it kept locking up from heat, so I then reformatted it as FAT32.  That made minimal to no difference, still slows down to similar sub-10MB/s speeds after a minute or two.

Posts: 1
Registered: ‎03-16-2019

Re: Ultra Flair 64GB USB 3.0 very slow write speeds

I have the same problems.Sometimes it gots hot and the writing rate goes down to 4000k Bit/sec (even it is not hot).It stops an wait for a while.then a little (or more) data transfer and it stops again.