On Thu, Dec 1, 2016 at 6:17 PM, Michael Paquier <michael.paquier@xxxxxxxxx> wrote:
On Thu, Dec 01, 2016 at 05:48:51PM +0200, Achilleas Mantzios wrote:
>
> Performance is the reason. You would benefit from moving pg_xlog to a
> different controller with its own write cache or to a different SSD with a
> write cache which is capacitor-backed. So in enterprise/server-class setups
> the above would boost the performance. Using the same SSD with a different
> partition won't give you much.
For performance, on-disk write pattern of data in pg_xlog is sequential
writes, while there will be likely random writes on the main data folder.
This is only the case if you have a write cache, or are doing bulk loads. With small transactions and without a write cache, the need for constant syncs totally destroys the benefits of sequential writes.
Cheers,
Jeff
