Re: BBU Cache vs. spindles - Mailing list pgsql-performance

From Kevin Grittner
Subject Re: BBU Cache vs. spindles
Date
Msg-id 4CC0513E0200002500036C68@gw.wicourts.gov
Whole thread Raw
In response to Re: BBU Cache vs. spindles  (Bruce Momjian <bruce@momjian.us>)
Responses Re: BBU Cache vs. spindles  (Bruce Momjian <bruce@momjian.us>)
Re: BBU Cache vs. spindles  (Andres Freund <andres@anarazel.de>)
Re: BBU Cache vs. spindles  (Greg Smith <greg@2ndquadrant.com>)
Re: BBU Cache vs. spindles  (Greg Smith <greg@2ndquadrant.com>)
Re: BBU Cache vs. spindles  (James Mansion <james@mansionfamily.plus.com>)
List pgsql-performance
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?

-Kevin

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