After much cogitation I eventually went RAID-less. Why? The only option for hardware RAID was SAS SSDs and given that they are not built on electro-mechanical spinning-rust technology it seemed like the RAID card was just another point of solid-state failure. I combined that with the fact that the RAID card limited me to the relatively slow SAS data-transfer rates that are blown away by what you get with something like an Intel NVME SSD plugged into the PCI bus. Raiding those could be done in software plus $$$ for the NVME SSDs but I already have data-redundancy through a combination of regular backups and streaming replication to identically equipped machines which rarely lag the master by more than a second.
On Wed, Nov 2, 2016 at 11:40 AM, Joshua D. Drake <jd@commandprompt.com> wrote: > On 11/02/2016 10:03 AM, Steve Atkins wrote: >> >> I'm looking for generic advice on hardware to use for "mid-sized" >> postgresql servers, $5k or a bit more. >> >> There are several good documents from the 9.0 era, but hardware has moved >> on since then, particularly with changes in SSD pricing. >> >> Has anyone seen a more recent discussion of what someone might want for >> PostreSQL in 2017? > > > The rules haven't changed much, more cores (even if a bit slower) is better > than less, as much ram as the budget will allow and: > > SSD > > But make sure you get datacenter/enterprise SSDs. Consider that even a slow > datacenter/enterprise SSD can do 500MB/s random write and read just as fast > if not faster. That means for most installations, a RAID1 is more than > enough.
Just to add that many setups utilizing SSDs are as fast or faster using kernel level RAID as they are with a hardware RAID controller, esp if the RAID controller has caching enabled. We went from 3k to 5k tps to 15 to 18k tps by turnong off caching on modern LSI MegaRAID controllers running RAID5.