From: "Wes Vaske (wvaske)" <wvaske@micron.com>
To: Kaixi Luo <kaixiluo@gmail.com>,
        Mark Kirkwood
	<mark.kirkwood@catalyst.net.nz>
CC: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Tuning guidelines for server with 256GB of RAM and
 SSDs?
Thread-Topic: [PERFORM] Tuning guidelines for server with 256GB of RAM and
 SSDs?
Thread-Index: Blbi1RQvqqe//YG0zUmGaPeS9HkTUvXq0zAAgAAvjQCAAALMcw==
Date: Thu, 7 Jul 2016 14:09:32 +0000
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 <577DE1C2.2010509@catalyst.net.nz>,<CAHo5iygNZ7UnaYh7hwLK+3T6e-g55wRpmTT8qdrrjfHfKRGD3Q@mail.gmail.com>
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?The Crucial drive does not have power loss protection. The Samsung drive d=
oes.


(The Crucial M550 has capacitors to protect data that's already been writte=
n to the device but not the entire cache. For instance, if data is read fro=
m the device during a garbage collection operation, the M550 will protect t=
hat data instead of introducing corruption of old data. This is listed as "=
power loss protection" on the spec sheet but it's not the level of protecti=
on that people on this list would expect from a drive)


________________________________
From: pgsql-performance-owner@postgresql.org <pgsql-performance-owner@postg=
resql.org> on behalf of Kaixi Luo <kaixiluo@gmail.com>
Sent: Thursday, July 7, 2016 2:49 AM
To: Mark Kirkwood
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] Tuning guidelines for server with 256GB of RAM and S=
SDs?

It's a Crucial CT250MX200SSD1 and a Samsung MZ7LM480HCHP-00003.

Regards,

Kaixi


On Thu, Jul 7, 2016 at 6:59 AM, Mark Kirkwood <mark.kirkwood@catalyst.net.n=
z<mailto:mark.kirkwood@catalyst.net.nz>> wrote:
On 06/07/16 07:17, Mkrtchyan, Tigran wrote:
Hi,

We had a similar situation and the best performance was with 64MB
background_bytes and 512 MB dirty_bytes.

Tigran.

On Jul 5, 2016 16:51, Kaixi Luo <kaixiluo@gmail.com<mailto:kaixiluo@gmail.c=
om>> wrote:


     Here are my server specs:

     RAID1 - 2x480GB Samsung SSD with power loss protection (will be used to
     store the PostgreSQL database)
     RAID1 - 2x240GB Crucial SSD with power loss protection. (will be used =
to
     store PostgreSQL transactions logs)


Can you tell the exact model numbers for the Samsung and Crucial SSD's? It =
typically matters! E.g I have some Crucial M550 that have capacitors and (o=
riginally) claimed to be power off safe, but with testing have been shown t=
o be not really power off safe at all. I'd be dubious about Samsungs too.

The Intel Datacenter range (S3700 and similar) are known to have power off =
safety that does work.

regards

Mark


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