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Re: SSD options, small database, ZFS

From: Amitabh Kant <amitabhkant(at)gmail(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: SSD options, small database, ZFS
Date: 2011-11-23 11:33:49
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
On Tue, Nov 22, 2011 at 11:41 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:

> Amitabh Kant wrote:> >
> >
> > On a slightly unrelated note, you had once (
> > said
> to
> > limit shared_buffers max to 8 GB on Linux and leave the rest for OS
> > caching. Does the same advice hold on FreeBSD systems too?
> Hard to say.  We don't know why this is happening but we are guessing it
> is the overhead of managing over one million shared buffers.  Please
> test and let us know.
> --
>  Bruce Momjian  <bruce(at)momjian(dot)us>
>  EnterpriseDB                   
I do have a FreeBSD 8.0 server running Postgresql 8.4.9 with 32 GB of RAM
(Dual Processor, SAS HD/RAID 10 with BBU for data and SAS HD/RAID 1 for
pg_xlog).  The current settings set effective cache size to 22 GB (pgtune
generated values). The server sees around between 500 to 1200 TPS and chugs
along pretty nicely. Sadly it's in production so I am not in a position to
run any tests on it. Changed values for postgresql.conf are:
maintenance_work_mem = 1GB # pg_generate_conf wizard 2010-05-09
checkpoint_completion_target = 0.9 # pg_generate_conf wizard 2010-05-09
effective_cache_size = 22GB # pg_generate_conf wizard 2010-05-09
work_mem = 320MB # pg_generate_conf wizard 2010-05-09
wal_buffers = 8MB # pg_generate_conf wizard 2010-05-09
checkpoint_segments = 16 # pg_generate_conf wizard 2010-05-09
shared_buffers = 3840MB # pg_generate_conf wizard 2010-05-09

I do have another server that is to go into production(48 GB RAM, dual
processor, Intel 710 SSD for data in RAID 1, SAS HD/RAID 1 for pg_xlog).
Apart from running pgbench and bonnie++, is there something else that I
should be testing on the new server? Greg's stream scaling seems to be for
linux, so not sure if it will work in FreeBSD.


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