Subject: Re: Sv: Sv: Re: Latest advice on SSD?
To: pgsql-performance@lists.postgresql.org
References: <VisenaEmail.35.c5e104eae07d6442.1634ef0e2ea@tc7-visena>
From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
Message-ID: <a7cf42e5-534a-ddfb-318c-cc8b39903b00@catalyst.net.nz>
Date: Sat, 12 May 2018 00:11:39 +1200
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On 11/05/18 23:23, Andreas Joseph Krogh wrote:

> På onsdag 09. mai 2018 kl. 22:00:16, skrev Andreas Joseph Krogh 
> <andreas@visena.com <mailto:andreas@visena.com>>:
>
>     På tirsdag 10. april 2018 kl. 19:41:59, skrev Craig James
>     <cjames@emolecules.com <mailto:cjames@emolecules.com>>:
>
>         On Tue, Apr 10, 2018 at 12:21 AM, Andreas Joseph Krogh
>         <andreas@visena.com <mailto:andreas@visena.com>> wrote:
>
>             På tirsdag 10. april 2018 kl. 04:36:27, skrev Craig James
>             <cjames@emolecules.com <mailto:cjames@emolecules.com>>:
>
>                 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.
>
>             With what arguments (also initialization)?
>
>         pgbench -i -s 100 -U test
>         pgbench -U test -c ... -t ...
>         -c  -t     TPS
>         5   20000  5202
>         10  10000  7916
>         20  5000   7924
>         30  3333   7270
>         40  2500   5020
>         50  2000   6417
>
>     FWIW; We're testing
>     this: https://www.supermicro.nl/products/system/1U/1029/SYS-1029U-TN10RT.cfm
>     with 4 x Micron NVMe 9200 PRO NVMe 3.84TB U.2 in RAID-10:
>     $ pgbench -s 100 -c 64 -t 10000 pgbench
>     scale option ignored, using count from pgbench_branches table (100)
>     starting vacuum...end.
>     transaction type: <builtin: TPC-B (sort of)>
>     scaling factor: 100
>     query mode: simple
>     number of clients: 64
>     number of threads: 1
>     number of transactions per client: 10000
>     number of transactions actually processed: 640000/640000
>     latency average = 2.867 ms
>     tps = 22320.942063 (including connections establishing)
>     tps = 22326.370955 (excluding connections establishing)
>
> Sorry, wrong disks; this is correct:
> 48 clients:
> pgbench -s 100 -c 48 -t 10000 pgbench
> scale option ignored, using count from pgbench_branches table (100)
> starting vacuum...end.
> transaction type: <builtin: TPC-B (sort of)>
> scaling factor: 100
> query mode: simple
> number of clients: 48
> number of threads: 1
> number of transactions per client: 10000
> number of transactions actually processed: 480000/480000
> latency average = 1.608 ms
> tps = 29846.511054 (including connections establishing)
> tps = 29859.483666 (excluding connections establishing)
> 64 clients:
> pgbench -s 100 -c 64 -t 10000 pgbench
> scale option ignored, using count from pgbench_branches table (100)
> starting vacuum...end.
> transaction type: <builtin: TPC-B (sort of)>
> scaling factor: 100
> query mode: simple
> number of clients: 64
> number of threads: 1
> number of transactions per client: 10000
> number of transactions actually processed: 640000/640000
> latency average = 2.279 ms
> tps = 28077.261708 (including connections establishing)
> tps = 28085.730160 (excluding connections establishing)
>
If I'm doing the math properly, then these runs are very short (i.e 
about 20s). It would be interesting to specify a time limit (e.g -T600 
or similar) so we see the effect of at least one checkpoint - i.e the 
disks are actually forced to write and sync the transaction data.

These Micron disks look interesting (pretty good IOPS and lifetime 
numbers). However (as usual with Micron, sadly) no data about power off 
safety. Do you know if the the circuit board has capacitors?

regards
Mark