| From: | "Albe Laurenz" <all(at)adv(dot)magwien(dot)gv(dot)at> |
|---|---|
| To: | "Jan Wieck *EXTERN*" <JanWieck(at)Yahoo(dot)com> |
| Cc: | "Tom Lane *EXTERN*" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [GENERAL] Undetected corruption of table files |
| Date: | 2007-08-31 12:34:09 |
| Message-ID: | D960CB61B694CF459DCFB4B0128514C2221576@exadv11.host.magwien.gv.at |
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| Lists: | pgsql-general pgsql-hackers |
Jan Wieck wrote:
> Computing a checksum just before writing the block will NOT detect any
> faulty memory or Postgres bug that corrupted the block. You will have
a
> perfectly fine checksum over the corrupted data.
>
> A checksum only detects corruptions that happen between write and
read.
> Most data corruptions that happen during that time however lead to
some
> sort of read error reported by the disk.
I have thought some more about it, and tend to agree now:
Checksums will only detect disk failure, and that's only
one of the many integrity problems that can happen.
And one that can be reduced to a reasonable degree with good
storage systems.
So the benefit of checksums is not enough to bother.
Yours,
Laurenz Albe
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