Re: Revisiting disk layout on ZFS systems

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On 04/28/2014 06:47 PM, Karl Denninger wrote:
What I am curious about, however, is the xlog -- that appears to suffer
pretty badly from 128k record size, although it compresses even
more-materially; 1.94x (!)

The files in the xlog directory are large (16MB each) and thus "first
blush" would be that having a larger record size for that storage area
would help.  It appears that instead it hurts.

The WAL is fsync'd frequently. My guess is that that causes a lot of extra work to repeatedly recompress the same data, or something like that.

- Heikki


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