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How long does this tool take to verify a real drive? "it only writes what’s necessary to test the drive" How does that actually work, wouldn't that mean the w
by bagels 2y ago
How long does this tool take to verify a real drive?
"it only writes what’s necessary to test the drive"
How does that actually work, wouldn't that mean the whole stated capacity would have to be written?
- jtriangle 2y agowrite 0001, read and confirm, repeat until drive is full. For a fake drive, it'll take awhile, because the underlying storage is much, much slower than it should be, often usb2 speeds. Realistically, this is just a test that satisfies curiosity without opening the drive. It's obvious when you have a fake drive because it won't benchmark anywhere near what it should.
- CaptainOfCoit 2y ago> For a fake drive, it'll take awhile Or, for any mid to large sized real storage. Writing/reading 64GB takes a while, fake or not
- deleted 2y ago[deleted]
- bagels 2y agoFrom what I understand, some of the fraudulent drives have firmware that just wrap the writes around to the beginning.
- ungamedplayer 2y agoI had or had one in my possession that did exactly this. Another writes above a certain size were simply discarded.
- sukmaagung 2y agoThe problem is the fake storage can just overwrite the new data on top existing data. Then you always confirm new data is correct because it broke the old ones. But something like 2TB micro SD when actually it only has 64GB capacity, that will be very long time waiting 2TB to fully written. How about write some file, then verify sometimes the new sometimes the old one, repeat until full. Write(0.h2w) Write(1.h2w) Read(1.h2w) Write(2.h2w) Write(3.h2w) Read(3.h2w) Read(2.h2w) Write(4.h2w) Write(5.h2w) Read(5.h2w) Write(6.h2w) Write(7.h2w) Read(7.h2w) Read(6.h2w) Read(4.h2w) Write(8.h2w) Write(9.h2w) Read(9.h2w) Write(10.h2w) Write(11.h2w) Read(11.h2w) Read(10.h2w) Write(12.h2w) Write(13.h2w) Read(13.h2w) Write(14.h2w) Write(15.h2w) Read(15.h2w) Read(14.h2w) Read(12.h2w) Read(8.h2w) ...Read(0.h2w)
- 10000truths 2y agoDefine hash(x) that takes an integer and returns a sector-sized hash. Define S = claimed total number of sectors. for(i=0; i<S; ++i) { write_sector(i, hash(i)) for(j=0; j<=i; ++j) { if(hash(j) != read_sector(j)) { return i } } } return S The above pseudo code will return the number of sectors the flash drive actually has.
- sroussey 2y agoWrite everything before read or you will just get back cached results.
- 10000truths 2y agoCache can only mask performance. It can't mask fraudulent reporting of storage capacity. At worst, the test above will return (size of write cache + size of actual storage), but a bargain-bin flash drive is going to have a very small (if any) write cache, so it's not going to overestimate by much.
- geocar 2y agoWhy would they only have a small write cache? You can map a lot of memory from pcie
- bagels 2y agoSure, so if the drive is genuine, or even one sector short (I recognize it's more typically a much larger fraction for the fraudulent drives), you'd still have to write to nearly the full stated capacity to verify. This approach though, seems to require reading the first sector many times.
- nullc 2y agoaccidentally quadratic. you just want two non-nested loops.
- 10000truths 2y ago