Obligatory “asking for a friend”. But no, like, if enemies of your state were possibly going to overrun a data center you rent a spot at but you still have some time, what’s the quickest way to, remotely, absolutely ruin any of the data on the disks? I can remember seeing old IBM "Death"Stars with the magnetic medium stripped clean. Don’t necessarily need that blatant a result, but say you didn’t have enough time to know if a basic dd /dev/{zero,random,urandom} /dev/mraid0 could run long enough to overwrite everything even just once, let alone a few times.
Alternatively, is there a file system which is purpose built for this sort of thing, where you send the array some sort of panic code – and I’m not considering drive encryption with a hardware or software key, whereas even if they were in place they are external to the disks themselves and thus at risk from external factors, rather than there being some command I can send to, well, if not crash the heads, then otherwise completely unravel the data structure in an irretrievable way with just one or two commands?
Say more about why you don’t want to use encryption for this?
This is easily done with encryption:
dd if=/dev/urnadom of=/dev/mraid0 oflag=sync bs=1M count=2. It’s thebs=1M count=2that makes it fast – you only need to clobber the first 2 megabytes of the disk, where the encryption keys are kept. (Yes, the keys are 2 entire megabytes! They’re stretched so that if the underlying hardware re-maps a sector to account for a physical media problem, only a small portion of the key is affected, rather than ‘the sector with the whole key’ being re-mapped. (Re-mapping sectors can leave mostly-but-not-entirely-inaccessible copies of old data laying around. We’d rather that happen to small chunks of a key rather than whole keys.))