Re: SSD gives disappointing speed up on OSX

Whilst the problem with the old filing system is correct. May be you want to ring out the best out of your current set up.

There are a few things you can do to improve these performance figures.

1) Turn off logging during insert.
2) Ensure logging is performed on a different disk than where db files.
3)Finally ensure read of insert statements and writes operations are on disks drives.

The last option should improve the performance figures as it *reduces* flushing of disk's cache in between operations.

-----Original Message-----
From: pgsql-general-owner(at)postgresql(dot)org [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Josh berkus
Sent: 03 February 2016 03:53
To: Bill Ross; pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] SSD gives disappointing speed up on OSX

On 02/02/2016 07:32 PM, Bill Ross wrote:
> I have a program that inserts 50M records of about 30 bytes each, with
> some simple indexing, using about 5 GB of disk, layout shown below.
> When I run the program without the inserts, it takes a few seconds to
> do just the calculation part.
>
> With inserts, it takes about 90 minutes to run on my macbook pro
> (2012) with a spinning disk and 8G memory. Since CPU was running at
> 40% idle, I figured this must be due to waiting on disk, so I swapped
> in an SSD. Now on the console I see 6 Mb/s negotiated link speed on
> disk, vs. 3 Mb/s before.

So, your basic problem is going to be that OSX doesn't have a decent filesystem to offer. HFS+ was created 18 years ago, and it was a hack on top of an older HFS. At its heart, it's still basically a DOS-era 16-bit filesystem. This means that as long as you are on Mac OS, you can assume that writes will be slow no matter how good your hardware is.

Supposedly you can still run ZFS on OSX, which might help you. I haven't done it, though.

--
--
Josh Berkus
Red Hat OSAS
(any opinions are my own)

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