Re: Latest advice on SSD?

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 <cjames@emolecules.com 
> <mailto:cjames@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.
>> ---------------------------------