From: | Stephen Frost <sfrost(at)snowman(dot)net> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | pgsql-hackers(at)postgresql(dot)org, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, Josh Berkus <josh(at)agliodbs(dot)com> |
Subject: | Re: Page Checksums |
Date: | 2011-12-19 17:13:50 |
Message-ID: | 20111219171350.GF24234@tamriel.snowman.net |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
* Andres Freund (andres(at)anarazel(dot)de) wrote:
> On Monday, December 19, 2011 03:33:22 PM Alvaro Herrera wrote:
> > > I do like the idea of putting the CRC info in a relation fork, if it can
> > > be made to work decently, as we might be able to then support it on a
> > > per-relation basis, and maybe even avoid the on-disk format change..
> > >
> > I think the main objection to that idea was that if you lose a single
> > page of CRCs you have hundreds of data pages which no longer have good
> > CRCs.
> Which I find a pretty non-argument because there is lots of SPOF data in a
> cluster (WAL, control record) anyway...
> If recent data starts to fail you have to restore from backup anyway.
I agree with Andres on this one.. Also, if we use CRC on the pages in
the CRC, hopefully we'd be able to detect when a bad block impacted the
CRC fork and differentiate that from a whole slew of bad blocks in the
heap..
There might be an issue there with handling locking and having to go
through the page-level lock on the CRC, which locks a lot more pages in
the heap and therefore reduces scalability.. Don't we have a similar
issue with the visibility map though?
Thanks,
Stephen
From | Date | Subject | |
---|---|---|---|
Next Message | Sushant Sinha | 2011-12-19 17:43:39 | Re: Postgres 9.1: Adding rows to table causing too much latency in other queries |
Previous Message | Stephen Frost | 2011-12-19 17:10:37 | Re: Page Checksums |