zeroing out part of an SDcard

[Chris Murphy]

On Aug 21, 2014, at 11:00 AM, Chris Adams <linux at cmadams.net> wrote:

> Once upon a time, Chris Murphy <lists at colorremedies.com> said:
>> However, quite a few sdcards don't respond to trim.
> 
> Do _any_ SD cards support TRIM?  I didn't think that was supported by
> the protocol at all.

It's a good question. fstrim spit back a message to the effect the device doesn't support trim. When I mkfs.btrfs, however, it reports trimming. And then when I dd read LBA's known to have previously contained data, I get zeros. *shrug* I don't actually know what's going on.

And then there's this:
https://www.sdcard.org/downloads/formatter_4/

"Using generic formatting utilities may result in less than optimal performance for your memory cards." So that implies they have something like trim, even if not the ATA variety. So I'm curious what this formatter is doing, and I'm also curious if we have an equivalent on linux or if in fact we get it already with normal mkfs; but then if that's true why does fstrim fail to do it.


Chris Murphy