The 512 Gb model is big enough that the SLC cache and performance is gonna be ok. What would worry me is the lifetime: individual 512 Gb 850 EVOs are rated at 150 Tb over 5 years. Compare that to the Intel S3710 - 400 Gb is rated at 8 Pb over 5 years. These drives are fast enough so that you *might* write more than 4x 150 = 600 Tb over 5 years...


In addition - Samsung are real cagey about the power loss reliability of these drives - I suspect that if you do lose power unexpectedly then data corruption will result (no capacitors to keep RAM cache in sync).


regards

Mark


On 11/04/18 13:39, Matthew Hall wrote:
The most critical bit of advice I've found is setting this preference:

https://amplitude.engineering/how-a-single-postgresql-config-change-improved-slow-query-performance-by-50x-85593b8991b0

I'm using 4 512GB Samsung 850 EVOs in a hardware RAID 10 on a 1U server with about 144 GB RAM and 8 Xeon cores. I usually burn up CPU more than I burn up disks or RAM as compared to using magnetic where I had horrible IO wait percentages, so it seems to be performing quite well so far.

Matthew Hall

On Apr 9, 2018, at 7:36 PM, Craig James <cja...@emolecules.com <mailto: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

--
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Craig A. James
Chief Technology Officer
eMolecules, Inc.
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