512GB Ultra Fit 3.2 Gen1 ultra slow

I bought the drive a couple of months ago and have found the write speeds to be no faster than 3.5MB per second. This is painfully slow when trying to copy a music album or movie. I have reformatted the drive to NTFS, but the speed has not improved.

I am ready to throw the drive into the trash, but hope that there is a simple solution to this problem.

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Check your security settings especially the antivirus ones. Some apps check every write to a device in your computer whether the write is for a file you are downloading or a file on your computer, which the app has already verified as safe, being written to another drive.

A dumb setting but frequently the default.

I have no issues writing to other flash drives.

The 512GB Ultra Fit 3.2 Gen1 USB drive has an impressively compact design, but its write speeds are disappointingly slow. Users report significantly lower performance than expected, which can be frustrating for transferring large files. Despite its high capacity and portability, the sluggish write speeds may limit its usefulness for tasks requiring quick data transfer. Consider this if you need speed over storage space.

Sadly, the write speeds are nowhere near the advertised rates. Sandisk should offer refunds or exchanges for these drives.

Well, I was told by a support rep that Sandisk does not quote Write speeds, only Read speeds. I can certainly see why! I have averaged under 2 MB/PS using this drive on three different computers.

It is said that we learn from our mistakes. I certainly have and will make future purchases for our company from those suppliers that are completely transparent with ALL relevant specifications.


I bought this drive 512GB capacity in 2021 i got the slower 130MB/s read not the new 400MB/s read. I put windows 10 in it with rufus to be used as main drive and yes it was slow for a while, i notice the issue was the active time being at 100% all the time, so i thought maybe if i update windows 10 and got the cumulative update, it took 8 hours but then active time was normal, now write speed is 15MB/s average while copying a 6.3GB image file from a usb ssd to the 512GB ultra fit sandisk that is runing windows 10, I also did update my laptop firmware to make things better. your issue may be active time on the drive that you check with task manager even if you insert the drive as removable storage but I’m not sure on this.

I am using Windows 11 Pro and the OS is always up-to-date. The folks at Sandisk told me that the write speeds should be between 10-15MB/s but I’ve been getting 1.5MB/s at best and frequently slower. I don’t really care about the read speeds, as there’s no point in getting 400MB/s reads if it takes a week to fill the drive with my content.

Sandisk has offered to replace the drive, but I will toss the replacement in the garbage if it exhibits the same behaviour. BTW, I tried writing to that drive on three different computers with the same results.

is not the drive is the nature of copying many small files as Im sure is your case and in my video example, when copying ex., 800 files each between 10kb-200kb such as pdf and html files, the write speed is very slow from ssd to ssd and even worse with usb drives but if your coying a 2GB 1 file it max out the drive, check my video, the sandisk ultra fit 400MB/s version has better write speed then the 130MB/s but small files copying is slow and for ssds too.

I have no patience for this kind of stuff. A drive that is supposed to write at 10-15mb/s should write at or close to those speeds all of the time. I have no issues with writing to SSDs at 10x those speeds, so it’s misleading advertising stating that a drive has 400mb/s “read” speeds when it takes forever to get data onto the drive in order to get the quoted read speeds.

I’ll look elsewhere for my next drive…

the 130MB/s drive has low write speed true, it can achieve 10-15MB/s from copying large files 50MB 6GB
try copying the files you were having slow speeds to from ssds and it will be better than the usb sandisk but not the advertised 540MB/s read 440MB/s write that ssds claim I bet you were copying similar to pdf html css js files, the speed from ssd to ssd will be mostly like 17-25MB/s when copying many small files, you might think the usb drive is broken when copying many small files takes forever but is normal for usb drives still.

I copied a few hundred FLAC files to a number of SSDs and they all copied at a rate of 90-120MB/s or about 100 times faster than copying them to the Sandisk. I don’t need write speeds of 400mb/s as my 16,000 FLAC files would copy to my SSD in just under 30 minutes instead of the 59 hours it took to copy them to the Sandisk.

As I said, this USB drive is useless to me and I will toss out the replacement if it exhibits similar ridiculous write speeds.


flacs from cds are probably 25-50MB u haven’t said how big they are if it took 49 hours then is probably the slowest it could write average 2MB/s but if the siz3s are 25-50mb it can’t take that long if the block size is 4kb i believe, try formating the drive not 4k 32k but 32MB block size manually using the format dos command.

It’s not going to happen. The drive will end up in the trash if it’s just as slow as the original which I returned. 'Nuff said.


(My FLAC files are 10-20MB each)