Re: Revisiting disk layout on ZFS systems

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