On Sun, Dec 10, 2017 at 4:00 PM, Wols Lists <antli...@youngman.org.uk> wrote: > > So the OP needs to be aware that, if his file is smaller than the chunk > size, then it *will* be recoverable from a disk pulled from an array, be > it md-raid or zfs. > > The question is, then, how big is a chunk? And if zfs is anything like > md-raid, it will be a lot bigger than the 512B or 4KB that a naive user > would think. >
I suspect the data is striped/chunked/etc at a larger scale. However, I'd really go a step further. Unless a filesystem or block layer is explicitly designed to prevent the retrieval of data without a key/etc, then I would not rely on something like this for security. Even actual encryption systems can have bugs that render them vulnerable. Something that at best provides this kind of security "by accident" is not something you should rely on. Data might be stored in journals, or metadata, or unwiped free space, or in any number of ways that makes it possible to retrieve even if it isn't obvious from casual inspection. If you don't want somebody recovering data from a drive you're disposing of, then you should probably be encrypting that drive one way or another with a robust encryption layer. That might be built into the filesystem, or it might be a block layer. If you're desperate I guess you could use the SMART security features provided by your drive firmware, which probably work, but which nobody can really vouch for but the drive manufacturer. Any of these are going to provide more security that relying on RAID striping to make data irretrievable. If you really care about security, then you're going to be paranoid about the tools that actually are designed to be secure, let alone the ones that aren't. -- Rich
