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From Jonathan Shook <jsh...@gmail.com>
Subject Re: Why are writes faster than reads?
Date Tue, 25 May 2010 22:33:17 GMT
Writes only have to write to the journal before returning. Reads have
to read potentially from several sources, including binary searches of
things that may or may not be cached anywhere.  The journal writes do
not involve much random disk IO, while the read activity does.

On Tue, May 25, 2010 at 11:53 AM, Tatu Saloranta <tsaloranta@gmail.com> wrote:
> On Tue, May 25, 2010 at 4:04 AM, Mark Greene <greenemj@gmail.com> wrote:
>> I'm fairly certain the write path hits the commit log first, then the
>> memtable.
>
> True, but that does not make them any less sequential -- journal logs
> are strictly sequential fast writes. Actual ordering occurs in memory,
> and results are eventually flushed from memtable to disk.
> There is no similar ordering for reads.
>
> -+ Tatu +-
>

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