On Thu, Oct 30, 2008 at 4:41 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> "Scott Marlowe" <scott.marlowe@gmail.com> writes:
>> On Thu, Oct 30, 2008 at 4:01 PM, Gregory Stark <stark@enterprisedb.com> wrote:
>>> I can't really see trusting Postgres on a filesystem that felt free to
>>> compress portions of it. Would the filesystem still be able to guarantee that
>>> torn pages won't "tear" across adjacent blocks? What about torn pages that
>>> included hint bits being set?
>
>> I can't see PostgreSQL noticing it. PostgreSQL hands the OS a 512byte
>> block, the OS compresses it and it's brethren as the go to disk,
>> uncompresses as they come out, and as long as what you put in is what
>> you get back it shouldn't really matter.
>
> I think Greg's issue is exactly about what guarantees you'll have left
> after the data that comes back fails to be the data that went in.
Sounds kinda hand wavy to me. If compressed file systems didn't give
you back what you gave them I couldn't imagine them being around for
very long.