> SSDs are generally slower than spinning at sequential IO and way faster at random.
Unreleased yet Seagate HDD boasts 480MB/s sequential read speed [1], and no HDD now can achieve that. Even SATA-3 SSD's could be faster than that for years now (550MB/s are quite typical), and NVME ones could be easily faster than 1GB/s and up to 3GB/s+. I'm curious to know where are you drawing these conclusions from? 1. https://blog.seagate.com/enterprises/mach2-and-hamr-breakthrough-ocp/ Dmitry Shalashov, relap.io & surfingbird.ru 2018-04-10 22:00 GMT+03:00 Aaron <aaron.wer...@gmail.com>: > RDBMS such as pg are beasts that turn random IO requests, traditionally > slow in spinning drives, into sequential. WAL is a good example of this. > > SSDs are generally slower than spinning at sequential IO and way faster at > random. > > Expect therefore for SSD to help if you are random IO bound. (Some cloud > vendors offer SSD as a way to get dedicated local io and bandwidth - so > sometimes it helps stablize performance vs. virtualized shared io.) > > A REASONABLE PERSON SHOULD ASSUME THAT UNBENCHMARKED AND UNRESEARCHED > MIGRATION FROM TUNED SPINNING TO SSD WILL SLOW YOU DOWN > > /Aaron > > > On Apr 10, 2018, at 12:54 PM, Benjamin Scherrey <scher...@proteus-tech.com> > wrote: > > You don't mention the size of your database. Does it fit in memory? If so > your disks aren't going to matter a whole lot outside of potentially being > i/o bound on the writes. Otherwise getting your data into SSDs absolutely > can have a few multiples of performance impact. The NVME M.2 drives can > really pump out the data. Maybe push your WAL onto those (as few > motherboards have more than two connectors) and use regular SSDs for your > data if you have high write rates. > > Meanwhile, if you're looking for strong cloud hosting for Postgres but the > speed of physical hardware, feel free to contact me as my company does this > for some companies who found i/o limits on regular cloud providers to be > way too slow for their needs. > > good luck (and pardon the crass commercial comments!), > > -- Ben Scherrey > > On Tue, Apr 10, 2018 at 9:36 AM, Craig James <cja...@emolecules.com> > wrote: > >> One of our four "big iron" (spinning disks) servers went belly up today. >> (Thanks, Postgres and pgbackrest! Easy recovery.) We're planning to move to >> a cloud service at the end of the year, so bad timing on this. We didn't >> want to buy any more hardware, but now it looks like we have to. >> >> I followed the discussions about SSD drives when they were first becoming >> mainstream; at that time, the Intel devices were king. Can anyone recommend >> what's a good SSD configuration these days? I don't think we want to buy a >> new server with spinning disks. >> >> We're replacing: >> 8 core (Intel) >> 48GB memory >> 12-drive 7200 RPM 500GB >> RAID1 (2 disks, OS and WAL log) >> RAID10 (8 disks, postgres data dir) >> 2 spares >> Ubuntu 16.04 >> Postgres 9.6 >> >> The current system peaks at about 7000 TPS from pgbench. >> >> Our system is a mix of non-transactional searching (customers) and >> transactional data loading (us). >> >> Thanks! >> Craig >> >> -- >> --------------------------------- >> Craig A. James >> Chief Technology Officer >> eMolecules, Inc. >> --------------------------------- >> > >
