How to securely wipe your ReadyNAS

mdgm wrote:

In any case unless you are paranoid or have a legal requirement to do a secure wipe, doing an ordinary factory default should be sufficient. With a 3 or more disk array, disposing of disks separately would also be something that could be done. With e.g. a 3 disk X-RAID array two disks would be needed to recover data and even then if you got those two disks and a factory default had been done on those two disks to wipe them you wouldn't recover data. Other things like connecting the disk up to a PC and formatting it using NTFS could be done. If a disk is formatted with NTFS most people would assume it was taken from a Windows Machine.

Just imagining paranoia for a moment... :twisted:

-I agree that an ordinary factory default should do the job for most users, since the raid array is completely rebuilt, which writes to every block on the disk (at least all the blocks in the raid partitions). AFAIK trying to recover the over-written data requires very special tools, and even then they probably don't get a lot of the data.

-Your separate disposal idea is much riskier. In your three disk example, if I had one of your disks (using XRAID-2) and was attempting forensic recovery I would have direct access to 1/3 of the array - 2/3 the blocks on the disk are data blocks, the rest are parity. The pattern is regular, so I could fairly easily tell where the data blocks were. So while I couldn't see all the data, I could see a fair amount of it. If you store passwords or personal information, there's a 33% chance it is on the disk I got from you. With X-RAID, I believe that the parity blocks are all on one drive. So in that case, if I happened to get a data disk I would have access to 50% of the data blocks, not 33%. And if it were a 2-disk array, it is mirrored, so I have all the data blocks.

My take - if you don't think reformatting a single disk volume is enough when you dispose of it, then you certainly won't feel comfortable with the separate disposal strategy. Even if you do think reformatting is enough, you could reasonably feel nervous about handing someone unknown a significant fraction of your data.

EDIT - if you are proposing separate disposal after a factory default, then of course that only reduces risk over a factory default. My paranoia was imagining simply removing the disks of an intact array and doing separate disposal.