Return-Path: X-Original-To: apmail-cassandra-user-archive@www.apache.org Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id D4304D772 for ; Tue, 4 Dec 2012 11:00:18 +0000 (UTC) Received: (qmail 77770 invoked by uid 500); 4 Dec 2012 11:00:16 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 77444 invoked by uid 500); 4 Dec 2012 11:00:15 -0000 Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm Precedence: bulk List-Help: List-Unsubscribe: List-Post: List-Id: Reply-To: user@cassandra.apache.org Delivered-To: mailing list user@cassandra.apache.org Received: (qmail 77428 invoked by uid 99); 4 Dec 2012 11:00:14 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 04 Dec 2012 11:00:14 +0000 X-ASF-Spam-Status: No, hits=1.5 required=5.0 tests=HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: domain of ravikumar.govindarajan@gmail.com designates 209.85.214.172 as permitted sender) Received: from [209.85.214.172] (HELO mail-ob0-f172.google.com) (209.85.214.172) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 04 Dec 2012 11:00:06 +0000 Received: by mail-ob0-f172.google.com with SMTP id za17so3956854obc.31 for ; Tue, 04 Dec 2012 02:59:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=JehdGvjUW/GtwK7V/MS7ZU2YahX66fiO65/XDx1n4UE=; b=jXWkmBbaWvFgvs4MT0pvqaUjejTZbDAiIjQczoEu+scX+qTiWuTS8NRGwyVMj+YnxM TS6yvi24jVcXevlTnEK96/tniNQ9xhqQv2JH5/55m2IRNtLnQqpXRvl1vfwj81bo37I3 GWUzhSkcK+bf8Fe1MQcceD36mvZ1CJLTSNNMiooh3bz9r5WLV3415ziERBON2Oc8vC7c svH/fYwtfaCVgvfJ3y86KmDLxc5N8HPbgN5JTsVEo8Bt214veptKxfAy3kWGAh34CuCJ OiIxzF6TkxU73Yhewt7FRYvgebObpMhMl9rq0eFKuCOZY9Qd2eK/CtFExKoYwnE/izYL xwDQ== MIME-Version: 1.0 Received: by 10.60.31.49 with SMTP id x17mr11301103oeh.33.1354618785602; Tue, 04 Dec 2012 02:59:45 -0800 (PST) Received: by 10.182.97.106 with HTTP; Tue, 4 Dec 2012 02:59:45 -0800 (PST) Date: Tue, 4 Dec 2012 16:29:45 +0530 Message-ID: Subject: Help on MMap of SSTables From: Ravikumar Govindarajan To: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=e89a8fb1ffc4859db504d004c3aa X-Virus-Checked: Checked by ClamAV on apache.org --e89a8fb1ffc4859db504d004c3aa Content-Type: text/plain; charset=ISO-8859-1 Our current SSTable sizes are far greater than RAM. {150 Gigs of data, 32GB RAM}. Currently we run with mlockall and mmap_index_only options and don't experience swapping at all. We use wide rows and size-tiered-compaction, so a given key will definitely be spread across multiple sstables. Will MMapping data files be detrimental for reads, in this case? In general, when should we opt for MMap data files and what are the factors that need special attention when enabling the same? -- Ravi --e89a8fb1ffc4859db504d004c3aa Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Our current SSTable sizes are far greater than RAM. {150 Gigs of data, 32GB= RAM}. Currently we run with mlockall and mmap_index_only options and don&#= 39;t experience swapping at all.

We use wide rows and si= ze-tiered-compaction, so a given key will definitely be spread across multi= ple sstables. Will MMapping data files be detrimental for reads, in this ca= se?

In general, when should we opt for MMap data files and = what are the factors that need special attention when enabling the same?

--
Ravi
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