| From: | "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql(at)mohawksoft(dot)com, "Hannu Krosing" <hannu(at)2ndquadrant(dot)com>, Decibel! <decibel(at)decibel(dot)org>, "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "Pg Hackers" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Block-level CRC checks |
| Date: | 2008-10-01 15:54:17 |
| Message-ID: | 36e682920810010854l5a4c4910u4a944ee447f4c343@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Oct 1, 2008 at 11:36 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I probably wouldn't compare checksumming *every* WAL record to a
>> single block-level checksum.
>
> No, not at all. Block-level checksums would be an order of magnitude
> more expensive: they're on bigger chunks of data and they'd be done more
> often.
That's debatable and would be dependent on cache and the workload.
In our case however, because shared buffers doesn't scale, we would
end up doing a lot more block-level checksums than the other vendors
just pushing the block to/from the OS cache.
--
Jonah H. Harris, Senior DBA
myYearbook.com
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