USB Ultra Flair SDCZ73 32GB/ 64GB 3.0 - Write Speeed only 25MB/s

I just bought usb 32GB and 64GB ultra flair cz73
I checked and read write speed on port usb 3.0 (sure enough driver)
And good read speed 130MB / s - 145MB / s
But the write speed is quite bad. 10 seconds beginning 60-80MB / s and descending rapidly then only 25 - 30MB / s
I used ISO, MKV to test copy and paste between USB and SSD
I hope there will be firmware fixes sandisk soon, I expect a higher write speed of at least 60MB / s
Thank sandisk


write speed is not stable
Tests ISO file on a 1GB capacity is always slow only 30MB / s
Conversely smaller than 1GB files are always fast 60MB / s

[1.png 2.png]]([/IMG])

The speed of the flash drive depends upon different factors. The factors includes the USB interface through which the flash drive is connected, the type of files being transferred and the operating system. Also, this  flash drive Read Speed can reach up to 150MB/s and it has no published Write Speed.

The max writing speed is 15x faster than a standard flahs drive (4MB / s)., That gives a maximum speed of 60MB/s which varies depending mainly on the size of the file, 

NOTE :  The SanDisk Ultra line does not ensure a stable sequential write speed (dont have the write speed on the packaging). If you want high-speed sequential write, you must switch to  SanDisk Extreme line.

The file system and the cluster size are also factors that influence the speed of large files. Test as follows:

CAUTION : This will remove all the contents of your USB flash driv e, be sure to select the correct removable drive letter and make a backup if necessary.

Download the SD Card Formatter Sofware  link:

Disconnect any USB device, and insert the USB flash drive, then open the “sd card formatter”, click on “Option” and select “Format size Adjustment: ON”,  and proceeds formatting.

The USB flash drive will be formatted in exFAT file system, You can make a new speed test now, I recommend the CrystalDiskMark:

Good Luck!

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format sd card On - 1g.png

format sd card On - 1g.png

1.png  2.png


write speeds improve, thank you very much

Not sure what kind of images you are trying to show but none of them appear.  Only a square with a triangle in it.


Write speed 30MB/s, Read Speed 130MB/s

i sure

Click on this URL to see what we see when you post images ronganh.

You need to post your images to a different service for people to see them here.

We have enabled picture uploads for the community. There was a permissions problem that has now been resolved. Going forward you do not need to upload to an external site.

Forum Admin


Hi admin

This is my picture in test


Write speed is 31MB/s :( 

i hope it x15 usb 2.0 speed is 60MB/s

I don’t understand why this thread is marked as “solved”, when it isn’t.

I found out the real reason with these write speed drops. This USB flash drive obviously uses some kind of cache, similarly as TLC SSDs use SLC cache. If you copy files that are smaller than cache size, you won’t notice any speed drop. But if you copy files that are larger than cache size, cache will fill up, and flash drive will continue writing to drive’s main slow NAND. You can verify that this is the case by cancelling of copying, and then immediatelly copying again - write speed will almost instantly fall down because drive hasn’t had the time to clear the cache yet, so the drives continues to write to main NAND instead of cache. If you cancel again, give the drive half a minute or a minute, and copy again, it will start at the full speed because now again it can write to cache, because it had enough time to clear it.

So, when you copy files to drive, it will first try to fill the cache. When the drive is idle, content from cache will be moved onto slow NAND.

I have 16 GB Ultra Flair drive - it seems that it has 384MB of cache (I suppose 3x128MB).

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An interesting observation marekic.

As for the thread being marked solved you will have to ask the OP.  He’s the one who marked it.

I have the same problem with Sandisk ultrafit 16 Gb; on USB 3.0 starts writing on 40 MB/sec and after 10 sec drops to 10 MB/sec and stabilize on it. On USB 2.0 port it stars at 20MB/sec and drops to 10MB/sec: I use Win 10 on I5 procesor, with USB 3.0 ports on MB.

So what is the truthș this is the real writing speed of this Sandisk flashdisk?

I bought a 32GB Ultra Fit one. Its cache is 1GB.
I think its the best and only correct answer I’ve found after some days!
I test your solution and you’re correct.
But it’s not efficient way to reach highest performance of flash! Why?
Let’s calculate!

You must let flash to SLEEP at least 30secs to clear its cache. If you don’t stop copying, about 600MB will copy within this time.
Until now, normal method is 600, and pause/resume method is 0. Come on! I went ahead :smiley:

After this, the flash will resume with about 60MB/s. But after about 15-20 seconds, its cache will fill up again! :frowning:
In this time, the normal way copies about 400MB!

0+1000 = 600+400 :smiley:

So we should be a satisfied good boy and don’t protest for speed drop of ultras -_-

The  “Up To” speed of 150MB/s are not specified to be Read or Write, refer to images

As the packaging states “Transfer a full-length movie in less than Blah blah Blah seconds”, calculations may be assummed the specified speed is for both Read and Write ? 

This may be construed to be misleading product information.

In the Far East where people are a sticker for details and nothing but exactness is acceptable or they’ll complain complain and complain some more, the Sandisk packaging DOES state both Read and Write information !

So the question to be asked with regard to Western packaging is “Why” ?

Ultra Flair 1.jpg Sandisk Ultra.jpg SanDisk-Ultra-Flair-CZ73 Read_Write Speed.jpg

Suck quality.

I bought a 64GB SanDisk Ultra USB 3.0 Flash Drive from Officework, pluged in only to find 57GB of storage. Thats 11% less than what is on the product label, outright cheeting.

I used have flash drives as small as 128Mb in the olden days, so I know there is no way there are 7GB worth of program system files in this stick. Max it’s a 58Gb stick, definetly not 64GB. Why is all this cheeting?

Not happy at all. I’m thinking of complaing to consumer afairs. What if you buy a bottle of Coke and find out it has 11% less juice than the lable says for some silly madeup reason? This is exatly like that, robbing is in plain sight.

@ amalpeiris -

Actual memory space is _ always _ less than advertised. And _ not _ just with SanDisk products, but ALL.

Find out why here.

i downloaded but the chs format size button is frezzed unable to click pls help me

MY Sandisk ultra USB 3.5 Speed is very low and speed been fluctuate lot since my last format

low speed.jpg