Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

XCalibur – the microSD in the stone

devpost.com

Post reply on HN
Print view View original

21–30 of 31 posts

Re: XCalibur – the microSD in the stone

#22

Post by digi_owl »

0x0 wrote: post #6
dmitrygr wrote: post #4

Some of the cheaper cards (and USB keys back in the day) sort of assume you'll use a single FAT[/32] partition and they understand the FAT and use it as poor man's TRIM information. They get super upset if you attempt anything that is not a single FAT[/32] partition. Some will actively forbid it by ignoring writes to the first sector of the disk and of the partition. Perhaps this is one of those cases? EDIT: technica…

Wow, that's scary. Imagine a file system that kinda sorta passes the "looks like fat" test but works differently, causing the card to TRIM randomly all over your files :O

Frankly "active" storage is all manner of scary when you get down to it, as you have not the first clue what the firmware etc sitting between the CPU and the actual bits can get up to.

Re: XCalibur – the microSD in the stone

#24

Post by zeusk »

0x0 wrote: post #9
boobsbr wrote: post #8

Earlier quoted context omitted.

what about using sync to flush changes to disk? does it flush the block device cache as well?

I think you have to play additional games with /proc/sys/vm/drop_caches then

Tried that as well, echo 3 > /proc/sys/vm/drop_caches

Re: XCalibur – the microSD in the stone

#25

Post by jkot »

I had exactly the same issue (except formatting my system).

SD card was broken, and it placed itself into read-only state for data recovery. I could delete files, but those would reappear. Formating would work until restart etc. Write cache was responsible for this weird magic.

I got card replaced as part of warranty.

Re: XCalibur – the microSD in the stone

#27

Post by zeusk »

kbaker wrote: post #13
stefs wrote: post #11

Jordan messes up and rm -rf / instead of rm -rf /dev/sdb slapstick classic

Err, even 'rm -rf /dev/sdb' wouldn't do what they want... Better to overwrite it completely with dd.

We used dd, gparted, parted to wipe not only the MBR and partition table but also the whole card.

Re: XCalibur – the microSD in the stone

#29

Post by zymhan »

rmellow wrote: post #28
zymhan wrote: post #12

I feel like there's some preface here that I'm missing.

Same here. I get that they're having trouble changing the FS on a MicroSD/writing an image on it. But what is XCalibur?

Maybe it's all some joke about how this one MicroSD card is just like excalibur? In that you can't get useful data out...

Re: XCalibur – the microSD in the stone

#30

Post by roytenberg »

zymhan wrote: post #29
rmellow wrote: post #28

Earlier quoted context omitted.

Same here. I get that they're having trouble changing the FS on a MicroSD/writing an image on it. But what is XCalibur?

Maybe it's all some joke about how this one MicroSD card is just like excalibur? In that you can't get useful data out...

All of the data was read-only, regardless of what adapter we put it in (we tried like five different ones). So you could retrieve the data that was baked onto it, but formatting the card was a lost cause.

So getting it to format was like trying to pull Excalibur out of the stone!

Post reply on HN