how to corrupt disk data for zfs testings

[berrywipe]

hi all...
I have a 3 disks raidz1 array with useless data. I'd like to test zfs recovery capabitlities by simulating silent corruption on one disk.
Of course I can mount the disk in another system (another pc or just a bootable cd), but if I could do it from freenas it would be quicker.
I have tried something like this:

Code:

[root@freenas] ~# dd if=/dev/random of=/dev/ada1 bs=4k count=100

but this was the result:

Code:

dd: /dev/ada1: Operation not permitted

any way to bypass this? Another method for writing raw data on disks would be welcome as well.

 

[StephenFry]

Using SARDU, I made a multi-boot USB stick with UltimateBootCD, Hiren's BootCD, etc. I then used a diskeditor I found on one of these "CDs" to muck around on a drive.

 

[berrywipe]

Yeah ultimate boot cd is exactly what I had tried when I was talking about "bootable CDs".
The reasons because of which I'd have liked an even faster method is that when accessing raw data o a disk you have to guess which sectors are actually in use by the raid, so it may take some tries.
Anyway I managed to hit some data sectors just yesterday and scrubbing worked like a charm, recovering 6 corrupted sectors spread over the disk.
Another time I corrupted sectors containing basic disk infos and the database was marked as degadated.
Off course resilvering fixed that.
ZFS rocks!