Re: Latest advice on SSD?

Well, I can give a measurement on my home PC, a Linux box running Ubuntu
17.10 with a Samsung 960 EVO 512GB NVME disk containing Postgres 10. Using
your pgbench init I got for example:

pgbench -c 10 -t 10000 test
starting vacuum...end.
transaction type: <builtin: TPC-B (sort of)>
scaling factor: 100
query mode: simple
number of clients: 10
number of threads: 1
number of transactions per client: 10000
number of transactions actually processed: 100000/100000
latency average = 0.679 ms
tps = 14730.402329 (including connections establishing)
tps = 14733.000950 (excluding connections establishing)

I will try to run a test on our production system which has a pair of Intel
DC P4600 2TB in RAID0 tomorrow.

On Tue, Apr 10, 2018 at 9:58 PM Charles Sprickman <css(at)morefoo(dot)com> wrote:

> On Apr 10, 2018, at 3:11 PM, Dmitry Shalashov <skaurus(at)gmail(dot)com> wrote:
>
> > 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?
>
>
> Yeah, that sequential info sounds weird.
>
> I’m only chiming in because I just setup one of those SoHo NAS boxes
> (Qnap) and it had both SSDs and HDDs installed. This was to be used for
> video editing, so it’s almost all sequential reads/writes. On 10Gb/s
> ethernet sequential reads off the cached content on the SSDs was somewhere
> around 800MB/s. These were non-enterprise SSDs.
>
> Charles
>
>
> 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(dot)werman(at)gmail(dot)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 <
>> scherrey(at)proteus-tech(dot)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 <cjames(at)emolecules(dot)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.
>>> ---------------------------------
>>>
>>
>>
>
>