On Wed, Sep 2, 2015 at 5:38 PM, Andres Freund <and...@anarazel.de> wrote: > If you additionally take into account hardware realities where you have > multiple platters, multiple spindles, command queueing etc, that's even > more true. A single rotation of a single platter with command queuing > can often read several non consecutive blocks if they're on a similar
Yeah. And in the case of solid state disks, it's really a much more simple case of, "synchronously reading from the disk block by block does not fully utilize the drive because of various introduced latencies". I find this talk of platters and spindles to be somewhat baroque; for a 200$ part I have to work pretty hard to max out the drive when reading and I'm still not completely sure if it's the drive itself, postgres, cpu, or sata interface bottlenecking me. This will require a rethink of e_i_o configuration; in the old days there were physical limitations of the drives that were in the way regardless of the software stack but we are in a new era, I think. I'm convinced prefetching works and we're going to want to aggressively prefetch anything and everything possible. SSD controllers (at least the intel ones) are very smart. merlin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers