From user-return-26200-apmail-cassandra-user-archive=cassandra.apache.org@cassandra.apache.org Wed May 16 12:41:18 2012 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 5F5BF97A1 for ; Wed, 16 May 2012 12:41:18 +0000 (UTC) Received: (qmail 67486 invoked by uid 500); 16 May 2012 12:41:16 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 67467 invoked by uid 500); 16 May 2012 12:41:16 -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 67457 invoked by uid 99); 16 May 2012 12:41:16 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 16 May 2012 12:41:16 +0000 X-ASF-Spam-Status: No, hits=-0.7 required=5.0 tests=RCVD_IN_DNSWL_LOW,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: domain of arodrime@gmail.com designates 209.85.212.172 as permitted sender) Received: from [209.85.212.172] (HELO mail-wi0-f172.google.com) (209.85.212.172) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 16 May 2012 12:41:09 +0000 Received: by wibhj8 with SMTP id hj8so2902460wib.7 for ; Wed, 16 May 2012 05:40:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :content-type; bh=dh6TcexqCWQQdYUqoBb2ggHivStOU7wZXK2C+0fRn7A=; b=v+C53g/fMFUHgKZCviTpbnh1TUFMtnMMnYBot/9C5SqGrbGY00fMqI83OMaJ8FCHu6 LJbFWO/bR6q6IkXtxpIXybaYBo9Dm7pUYsFvV1yvrklRBJ55JlX9kPnQSci+EvAAyijR Hl+lJPVU1E58dZzUUyTPmKGgfQ1le/ElH5/jBuNVDGzc1rugfY8SrWWsjDOsD34BeglK /pzFk+b7ojK2swDIw2PIeldIuMfYsu/CwVEZ534Bfn/s6S3+YF291y5hy4aQfCdYi3eV Uodb2KYVxPvsImkv08CkiZ9PyUdnQFivWV00VM4rmx3zgmR+Poy2+xauC7Dfjx1EDO8l Gmeg== Received: by 10.180.109.197 with SMTP id hu5mr7683983wib.8.1337172048535; Wed, 16 May 2012 05:40:48 -0700 (PDT) MIME-Version: 1.0 Received: by 10.223.120.78 with HTTP; Wed, 16 May 2012 05:40:26 -0700 (PDT) In-Reply-To: <1620C181-AEFE-40A8-81B6-4909CE87AA92@thelastpickle.com> References: <1620C181-AEFE-40A8-81B6-4909CE87AA92@thelastpickle.com> From: Alain RODRIGUEZ Date: Wed, 16 May 2012 14:40:26 +0200 Message-ID: Subject: Re: Tuning cassandra (compactions overall) To: user@cassandra.apache.org Content-Type: text/plain; charset=ISO-8859-1 X-Virus-Checked: Checked by ClamAV on apache.org Using c1.medium, we are currently able to deliver the service. What is the the benefit of having more memory ? I mean, I don't understand why having 1, 2, 4, 8 or 16 GB of memory is so different. In my mind, Cassandra will fill the heap and from then, start to flush and compact to avoid OOMing and fill it again. The memory used inside the heap will remains close to the max memory available, therefore having more or less memory doesn't matter. I'm pretty sure I misunderstand or forget something about how the memory is used but not sure about what. Can you enlighten me about this point ? If I understand why the memory size is that important I will probably be able to argue about the importance of having more memory and my boss will probably allow me to spend more money to get better servers. "There are some changes you can make to mitigate things (let me know if you need help), but this is essentially a memory problem." I'm interested a lot in learning about some configuration I can use to reach better peformance/stability as well as in learning about how Cassandra works. Thanks for the help you give to people and for sharing your knowledge with us. I appreciate a lot the Cassandra community and the most active people keeping it alive. It's worth being said :). Alain