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Re: Block-level CRC checks

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Aidan Van Dyk <aidan(at)highrise(dot)ca>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, 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 20:16:13
Message-ID: 28254.1222892173@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Aidan Van Dyk <aidan(at)highrise(dot)ca> writes:
> One possibility would be to "double-buffer" the write... i.e. as you
> calculate your CRC, you're doing it on a local copy of the block, which
> you hand to the OS to write...  If you're touching the whole block of
> memory to CRC it, it isn't *ridiculously* more expensive to copy the
> memory somewhere else as you do it...

That actually seems like a really good idea.  We don't have to increase
the buffer locking requirements, or make much of any change at all in
the existing logic.  +1, especially if this is intended to be an
optional feature (which I agree with).

			regards, tom lane

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