Re: Latest advice on SSD?

> 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(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.
>> ---------------------------------
>>
>
>