Will mediainit permit re-use of degaussed disks?

[mvpel]

We have a batch of hard drives that we'd like to securely wipe and store as spares. Is the mediainit command capable of returning thoroughly degaussed disk drives to a usable condition?

I ask because degaussing with re-init would be a lot quicker, I suspect, than doing a bcwipe of dozens of disks.

[Michael Steele_2]

Here's a fellow that uses mediainit after degaussing

http://www.brandonhutchinson.com/Wiping_HP-UX_disks.html

[James R. Ferguson]

Hi:

If you are running a recent 11.31 (update-3 or later, I believe) then 'mediainit' has a scrub option ('-S') that obviates de-gaussing or using 'dd' to wipe disks.

Regards!

...JRF...

[Steven Schweda]

> [...] degaussing with re-init [...]

"Degaussing" normally involves the use of
either a very high temperature or a very
strong electromagnet. Either of these
methods could render a disk drive unusable,
especially the high temperature method.

Every harmless scheme to erase data on a disk
drive involves writing new data to the drive,
typically many times, which is not the same
as "degaussing" it.

> [...] securely wipe [...]

Define "securely". Destroying the drives can
be pretty secure. (It can be done pretty
quickly, too.) Trying to overwrite the data
until they can't be read by anyone at any
cost may be impossible.

[mvpel]

Michael - the link you provided doesn't mention degaussing, just doing a mediainit on disks to be returned from a bootable CD.

To be more specific, Steve, I'm talking about magnetic degaussing.

Normally when we take down a system we'll drill and shred the drives, but we have a batch of old systems for which replacement drives are hard to come by, and getting harder by the day.

And we have a batch of old replacement drives for HP-UX 11.11 (not 11.31, unfortunately) with rather old chain of custody records from people who are no longer here, if you get my drift.

So, we'd like to make a new chain-of-custody entry for a nice clean slate at a fixed date.

The approved (in the security plan) harmless scheme for clearing the drives, BCwipe, takes one of our systems out of production for quite a long time, since we don't have a spare system which is compatible with these older drives, and we can't put the old disks into a production system due to data segregation requirements.

So if we could just do a nice solid magnetic degauss, which takes the disk back to square one in a matter of seconds, we can then put the disk into one of the production systems without any data segregation issues, make the proper chain-of-custody entries, and away we go with a metainit.

My concern, though, is whether a magnetic degauss may damage or dislodge internal mechanisms of the disk or otherwise render it un-mediainit-able.

[James R. Ferguson]

Hi (again):

Since you aren't (yet) running 11.31, I'd simply use 'dd' with '/dev/zero' or '/dev/urandom' as input and make your own n-passes.

Use the raw disk device files so that you bypass the Unix buffer cache and use a large blocksize:

# dd if=/dev/zero of=/dev/rdsk/cXtYdZ bs=1024k

# dd if=/dev/urandom of=/dev/rdsk/cXtYdZ bs=1024k

When the end of the device is reached, 'dd' will simply stop. Use as many iterations as you see fit. All of the above script very simply in a shell.

This isn't destructive to the disk or any physical mechanism and is going to prevent all but the very determined from reading any old data. Then, when you have no further requirements for the old hardware, drill, spindle and bath in acid until your heart's content.

Regards!

...JRF...

[mvpel]

Thanks for your input folks, I appreciate it. What I was trying to avoid is the time-consuming process of individually nuking each sector of the disk by nuking all the sectors at once with the degausser.

But it looks like the approach we're going to take, given the potential stresses imposed by a magnetic degauss and the uncertainties around reinitializing such a disk, is to go the BCwipe route.

We may be able to pull a couple of spare enclosures out of the closet and hook them up and see if we can't run BCwipe on 63 disks at the same time without crushing the Fibre Channel adapters too hard. We'll just have to muscle through the productivity hit of having to take the wiping machine out of production for the duration.

[Steven Schweda]

> [...] potential stresses imposed by a
> magnetic degauss [...]

Stresses, shmesses.

http://en.wikipedia.org/wiki/Degaussing

Look for "Irreversible damage to some media
types".

One might run the experiment on one
(low-value) disk, if actual proof were
desired.

[mvpel]

I'm sure loss of servo tracks would be stressful for the drive firmware. Thanks for the reference!

[Greybeard]

hey Mpvel, you say the disks are hard to come by, drop me a mail with the specs and I may be able to help, we are a data storage specialist based in UK and USA and have a warehouse full of obscure stuff :)

[Louis Henninger_1]

Keep in mind:

Even with BC Wipe,(or equal) you can not cross boundaries...at least in the government space.

you can always go up "unclass to class", but not down.

Regards,

Louis

[troy12n_1]

Using degausing is rather archaic, use DBAN (Darik's boot and nuke), its freeware and potentially more thorough than degausing...

http://www.dban.org/

[mvpel]

We've been using BCwipe to bring disks from one classified IS to another, and that seems to be working out reasonably well, in spite of the severe time penalty. If the disk can make it through a multi-pass wipe without collapsing into a quivering heap of I/O and non-medium errors, we can be reasonably assured it will work out in a new system. We also seem to only be able to wipe five disks per enclosure at any one time - perhaps a Fibre Channel bandwidth issue.

We're using A7289 disks with DS2405 disk arrays on nearly all the systems.