From: Ravi Krishna <s.ravikrishna@aim.com>
To: tgl@sss.pgh.pa.us
Cc: pgsql-admin@postgresql.org
Subject: Re: WAL and O_DIRECT
Date: Thu, 14 May 2015 12:07:04 -0400
Message-ID: <14d532dde85-2108-310a1@webstg-m03.mail.aol.com> (raw)
In-Reply-To: <21483.1431618933@sss.pgh.pa.us>
References: <21483.1431618933@sss.pgh.pa.us>
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>> However our DB2 folks are raising a concern that PG WAL writes may not be crash safe, unless we are using
>> write back technology in SAN or SSD , which we are using.
> What's your point exactly? If the underlying hardware does not provide durable writes, there's
> nothing PG (or DB2) can do to fix that.
Am I right in concluding that PG WAL writes without underlying h/w caching is not crash proof.
Fortunately these days caching is ubiquitous in all SSD/SAN technology. Both Oracle and DB2 always open WAL
logs in O_DIRECT. Is this thinking outdated with modern technology which caches writes. Wonder why Oracle/DB2
are not making O_DIRECT optional. I am sure it will increase the write performance.
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To: pgsql-admin@postgresql.org
Cc: s.ravikrishna@aim.com, tgl@sss.pgh.pa.us
Subject: Re: WAL and O_DIRECT
In-Reply-To: <14d532dde85-2108-310a1@webstg-m03.mail.aol.com>
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