Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eYy6L-0006Uz-6Y for pgsql-general@arkaria.postgresql.org; Tue, 09 Jan 2018 17:54:17 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eYy6J-0008Pg-RG for pgsql-general@arkaria.postgresql.org; Tue, 09 Jan 2018 17:54:15 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1eYy6J-0008P5-Jv for pgsql-general@lists.postgresql.org; Tue, 09 Jan 2018 17:54:15 +0000 Received: from tamriel.snowman.net ([96.255.250.162]) by magus.postgresql.org with esmtp (Exim 4.89) (envelope-from ) id 1eYy6G-00080e-AG for pgsql-general@lists.postgresql.org; Tue, 09 Jan 2018 17:54:14 +0000 Received: by tamriel.snowman.net (Postfix, from userid 1000) id 066FA5F79C; Tue, 9 Jan 2018 12:54:10 -0500 (EST) Date: Tue, 9 Jan 2018 12:54:10 -0500 From: Stephen Frost To: Rakesh Kumar Cc: "pgsql-general@lists.postgresql.org" Subject: Re: data-checksums Message-ID: <20180109175410.GH2416@tamriel.snowman.net> References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="w6gGg34HLhiRwcqo" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Precedence: bulk --w6gGg34HLhiRwcqo Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Greetings, * Rakesh Kumar (rakeshkumar464@mail.com) wrote: > --data-checksums > Use checksums on data pages to help detect corruption by the I/O system t= hat would otherwise be silent. Enabling checksums may incur a noticeable pe= rformance penalty. This option can only be set during initialization, and c= annot be changed later. If set, checksums are calculated for all objects, i= n all databases. > =3D=3D=3D=3D >=20 > If I understand it correctly, the performance penalty is when the blocks = are written to the disk by the background writer and/or during checkpoint. = Given that the process is async and application does not wait on it, is th= e performance penalty really a big concern. There's also a hit when pages are read back in, since we need to calculate the checksum and verify it hasn't changed. That said, imv anyway, the performance hit is small and having checksums is well worth it. Thanks! Stephen --w6gGg34HLhiRwcqo Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCgAGBQJaVQHCAAoJEO1sijiDR2RVieEQALv0wiHJZ9gbSmWwNryehXEg pH3ybO0SNs2TA2XZw5vr71Zw/y9/xFTdSocyFZsWPXTcde0ytDn2/ZLq0OxwxWr7 i+gEHILTClcubEB596vwB0SCN30nrHw0XDSwfy6LP/N3hKvHNIBUIvsaj5py6tkZ xxI7XHN/rLyahItoMjgiGu2TFWFvob2NmegUhFTHcFxe17iyMD56SptYpRb86v/w +LFhgUL5yxWJPiKp2RF9xaRXhfTxYyzmDzuJqwhM1GrmZcPq9Brk6ZEVhHYh2Iv6 KA+2zDoL7J89ou5hVtnf4q+skY1JEEIFfqBZvDJXi4jjFddqMSziUKYMrnBN7Ejs MnFA4JHJ5x86pAO+wyEg6xuC25DFm1bTis7DK5/wOgZ+hTdlX1GArtKMtK4cxUr8 89RS7+v2yYdUvOK4TxA1hkH0fdKPhL0eMemeV9WnL/9yiKbXP83ly9IAPlXtgfG7 Vp56r32IK5fYa3vy0sEA8Gc6zjkkTFwjz9lMeiqEOb+Qm1jPMjhp/q/lqcUWk6Xf nMIWV/ceaa/UyF5GQiEnr6hh4PQnLQTTFDC0XyTbh4YEMSpjK7IqCcZ9gQ4a2+id CxaX7n22jqOtf17NyA0LbCv3Mih45LtCXgj9KNeqOyxGiafGAiJtxfX3SytKwYzz F5nYXhIBXx1FvWe/m5Sx =5b27 -----END PGP SIGNATURE----- --w6gGg34HLhiRwcqo--