I purchased a SanDisk 512GB Ultra Luxe USB 3.2 Gen 1 Flash Drive with the markings: “SDCZ74-512G-GAM46” on it about a year ago, and it worked “fine” but the write speed was much slower than it should be (around 4 MB/s in sustained writes) so backups to the drive were taking 4-8 times longer than they should.

I eventually got tired of this, and sent it back to SanDisk for a warranty replacement, and I’m happy to report that the replacement Ultra Luxe drive [USB 3.1 Flash Drive] with markings “512GB  BR200357930W SDCZ74 Made in Malaysia” works much better. [27 MB/s sustained writes on a 252 GB file system, 90+ MB/s reads on a 2.8 GB file.]

There are two remaining downsides that keep this from being the perfect “keyring” backup drive. 1) It gets very hot to the touch (I’ve measured temps as high as 124 F when writing for multiple hours….).  2) I wish that the hole on the back of the drive was just slightly larger. If you orient it correctly on a keyring, it will fit snugly against other keys, but the hole isn’t large enough to let it “rotate” on the keyring so the ring can rotate and fold flat in your pocket.

So, if you have a SanDisk flash drive that isn’t working as fast as it should, try the warranty replacement process. Here is a photo of the back of the good drive: