Re: [PATCH 0/6] block: add support for REQ_OP_VERIFY

Keith Busch
2022-12-03T15:40:01Z

On Fri, Dec 02, 2022 at 05:33:33PM +0000, Clay Mayers wrote:
> >
> > As long as the protocols don't provide proof-of-work, trying this
> > doesn't really prove anything with respect to this concern.
>
> I'm out of my depth here, but isn't VERIFY tightly related to PI and
> at the heart of detecting SAN bit-rot? The proof of work can be via
> end-to-end data protection. VERIFY has to actually read to detect bad
> host generated PI guard/tags. I'm assuming the PI checks can be
> disabled for WRITE and enabled for VERIFY as the test.

I suppose if you happen to have a PI formatted drive, you could WRITE
garbage Guard tags with PRCHK disabled, then see if VERIFY with PRCHK
enabled returns the Guard Check Error; but PI is an optional format
feature orthogonal to the VERIFY command: we can't count on that format
being available in most implementations.