tool for mapping away bad blocks on an external disk

Warren Block wblock at
Mon Apr 18 22:21:28 UTC 2016

On Mon, 18 Apr 2016, Kevin P. Neal wrote:

> On Mon, Apr 18, 2016 at 08:55:34AM +0200, Matthias Apitz wrote:
>> Thanks for all the hints; I started last night with overwriting the full
>> disk with:
>> # dd conv=noerror if=/dev/zero of=/dev/da0 bs=1m
> Just curious: Does anyone know what happens when there is not enough space
> at the end of a disk (or tape) to write the entire block? Does a partial
> block get written, or does no block get written?

It writes the partial block.  Or at least I've never bothered doing 
anything special, and the checksums work out.

> It is because I don't know what happens that I usually pick a block size
> that is mathematically factored out from the number of blocks on the disk
> (and then multiplied by the number of bytes in a block obviously).

You work too hard. :)

More information about the freebsd-questions mailing list