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From: Florian Weimer <fweimer@bfk.de>
To: Chris Browne <cbbrowne@acm.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: Making the most of memory?
Date: Fri, 25 Jan 2008 09:18:41 +0100
Message-ID: <824pd28gim.fsf@mid.bfk.de> (raw)
In-Reply-To: <60r6g7kxax.fsf@dba2.int.libertyrms.com>
References: <4796BE84.9030803@centriccrm.com>
	<dcc563d10801222120q78e390dbj2b884eca729c2975@mail.gmail.com>
	<B30794E6-CD2A-43C1-B431-E24B56FBFB1D@concursive.com>
	<dcc563d10801231044p1dba892r9b8bf1269395f068@mail.gmail.com>
	<47979C15.3040406@burntmail.com>
	<4797A8B3.5040605@janestcapital.com>
	<Pine.LNX.4.64.0801241405020.4642@aragorn.flymine.org>
	<82tzl39u55.fsf@mid.bfk.de>
	<60r6g7kxax.fsf@dba2.int.libertyrms.com>

* Chris Browne:

>> A dedicated RAID controller with battery-backed cache of ssuficient
>> size and two mirrored disks should not perform that bad, and has the
>> advantage of easy availability.
>
> That won't provide as "souped up" performance as "WAL on SSD," and
> it's from technical people wishing for things that some of those
> things actually emerge...

For WAL (I/O which is mostly sequential), the proposed approach isn't
that bad.  You can easily get more than 15,000 write transactions per
second, with a single thread.  Good luck finding a SSD NAS with a
60 usec round-trip time. 8->

Something which directly speaks SATA or PCI might offer comparable
performance, but SSD alone isn't sufficient.

-- 
Florian Weimer                <fweimer@bfk.de>
BFK edv-consulting GmbH       http://www.bfk.de/
Kriegsstraße 100              tel: +49-721-96201-1
D-76133 Karlsruhe             fax: +49-721-96201-99



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