| From: | Bruno Wolff III <bruno(at)wolff(dot)to> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Greg Stark <gsstark(at)mit(dot)edu>, Russell Smith <mr-russ(at)pws(dot)com(dot)au>, josh(at)agliodbs(dot)com, Postgres Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Checkpoint cost, looks like it is WAL/CRC |
| Date: | 2005-07-07 04:16:54 |
| Message-ID: | 20050707041654.GA14153@wolff.to |
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| Lists: | pgsql-hackers |
On Wed, Jul 06, 2005 at 21:48:44 +0100,
Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
> We could implement the torn-pages option, but that seems a lot of work.
> Another way of implementing a tell-tale would be to append the LSN again
> as a data page trailer as the last 4 bytes of the page. Thus the LSN
> would be both the first and last item on the data page. Any partial
> write would fail to update the LSN trailer and we would be able to see
> that a page was torn. That's considerably easier than trying to write a
> torn page tell-tale to each 512 byte sector of a page as SQLServer does.
Are you sure about that? That would probably be the normal case, but are
you promised that the hardware will write all of the sectors of a block
in order?
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