getting garbage faster using FreeBSD?

Kris Kennaway kris at
Mon Feb 19 19:51:44 UTC 2007

On Mon, Feb 19, 2007 at 08:40:37PM +0100, Volker wrote:
> Hi!
> For my dentist I'm currently in the process of destroying some tape
> cartridges (SLR7) and also two hard disks (147G SCSI).
> As I started for the tapes, I've used dd to fill the tape with
> random garbage. Just a simple `dd if=/dev/random of=/dev/nsa0'.
> The tape sits there since 48 hours writing a block of data every
> other minute and still didn't fill up the tape completely. The
> system this is running on is a P-4 3GHz machine using FreeSBIE 2.0
> (6.2-RELEASE based).
> I suspect this to be a slow /dev/random.

This sounds odd to me, I get 18-20MB/sec sustained read performance
from /dev/random on this 2GHz system, which is probably faster than
your tape write speed.

> Is there any chance to speed up /dev/random? Would a hifn
> accelerator card help here to get FreeBSD produce garbage faster?
> As there is medical data on all media I really need garbage
> (/dev/zero wouldn't be enough for data security as this might get
> recovered).

Neither would a single pass with /dev/random, but you presumably knew


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