Is destroying data on a pool safe for sale

[Crispin]

Hi folks,

I am selling my NAS and all it's disk on fleabay. I've deleted the pool (was not an encrypted pool) and ticked the destroy-data button. Is it safe to sell the disks to someone?

I'm doing a dd /zero on the disks but at 4TB disks, 12 hours later it's only 320GB done. This makes me think it's going to take 125 hours!


C

 

[NugentS]

No destroy data is not safe for sale.

 

[Patrick M. Hausen]

I'm doing a dd /zero on the disks but at 4TB disks, 12 hours later it's only 320GB done. This makes me think it's going to take 125 hours!

What blocksize are you using? With 1 M, i.e. dd if=/dev/zero of=/dev/adaX bs=1m, it should not take that long. If you don't specify a block size, the default is one block, i.e. 512 bytes. Which might explain why it's so slow for you.

 

[Crispin]

I realised I was had not specified the block size and it was running at around 7MiB/s which was horrendous. I then found that a block size of 100M ran around 125MiB/s which is a lot better. Basically any block size larger than default was largely better.
It's running now, 10 hours in and I have around 10 hours to go. Not end of the world.

I also noticed the server this is running on is CPU constrained (HP Microserver Gen 7) and PV + dd are keeping it busy across 3 disks, 99%.

 

[Ericloewe]

Just to clarify: A zpool destroy is so trivial to undo there's a zpool import option to do so. TrueNAS also nukes the partition table, but that's also trivial to recreate.