On 12/11/12 05:55, Greg Smith wrote:
The only guarantee I see that we can give for online upgrades is that
after a VACUUM CHECKSUM sweep is done, and every page is known to both
have a valid checksum on it and have its checksum bits set, *then* any
page that doesn't have both set bits and a matching checksum is
garbage. Until reaching that point, any old data is suspect. The
idea of operating in an "we'll convert on write but never convert old
pages" can't come up with any useful guarantees about data integrity
that I can see. As you say, you don't ever gain the ability to tell
pages that were checksummed but have since been corrupted from ones
that were corrupt all along in that path.
You're right about that, but I'd just like some rough guard against
hardware/OS related data corruption.
and that is more likely to hit data-blocks constantly flying in and out
of the system.
I'm currently running a +2TB database and the capabillity to just see
some kind of corruption earlier
rather than later is a major benefit by itself. Currently corruption can
go undetected if it just
happens to hit data-only parts of the database.
But I totally agree that the scheme described with integrating it into a
autovacuum process would
be very close to ideal, even on a database as the one I'l running.
--
Jesper
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