Re: BBU Cache vs. spindles

On Thursday 21 October 2010 21:42:06 Kevin Grittner wrote:
> Bruce Momjian <bruce@momjian.us> wrote:
> > I assume we send a full 8k to the controller, and a failure during
> > that write is not registered as a write.
>
> On what do you base that assumption?  I assume that we send a full
> 8K to the OS cache, and the file system writes disk sectors
> according to its own algorithm.  With either platters or BBU cache,
> the data is persisted on fsync; why do you see a risk with one but
> not the other?
At least on linux pages can certainly get written out in < 8kb batches if
youre under memory pressure.

Andres