On Wed, Jul 8, 2015 at 1:48 PM, Kaza Kore <dj_kaza@xxxxxxxxxxx> wrote: > Date: Wed, 8 Jul 2015 18:37:04 +0000 > From: f.rech@xxxxxxxx > To: dj_kaza@xxxxxxxxxxx > Subject: Re: OT: Bash help to check new USB keys. > > It's not a full testing of a flash device I'm worried about, especially as > they are new, I just want to know they really are the size they report as > being... > > Dale. > > Probably GParted will tell you that, > HTH, > Fred > > Except the likes of GParted, df, udisks etc are exactly what I don't trust! > I have read too many reports of people buying say a 128GB usb drive, copying > loads of data onto it and later discovering everything after say 8 or 16GB > isn't really there! Somehow they fake the part (ToC? MBR?) which the > computer reads the size of the drive from and seems (at least in Doze-land, > where most of these reports are from, but then again so is most the computer > world) that the system even reports having written the files correctly and > they show up in the table of contents and in your file explorer as you would > expect. Hence I want to actually write data until the drive is near full and > do an md5sum on the files I have written. It's only a single write of the > few thousand they should be usable for and I plan to use them predominantly > as back-up storage so I don't envisage lots of erase and re-writes over > their lifetime. Basic drive integrity isn't a worry. Being sold dodgy, fake > components which report the wrong size is. > > I did wonder if doing something as simple as a full (rather than Quick) > format to the likes of ext4 might catch out something like this too... > > Dale. Programmers like to report size in gibi bytes, and manufacturers almost always use giga bytes. https://en.wikipedia.org/wiki/Gibibyte There's about a 7.5% difference between the units. So, the units can make it look like you're losing 8GB off a 128GB disk, or 16GB off a 256GB disk. I have to explain this to people all the time... no.... the software is wrong according to definitions, so you have to add/subtract x% to get your command right. So, do some math and see if you can explain the discrepancies with units. Chuck _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
