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 675A1CBC1 for ; Fri, 19 Jul 2013 18:18:49 +0000 (UTC) Received: (qmail 72409 invoked by uid 500); 19 Jul 2013 18:18:46 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 72268 invoked by uid 500); 19 Jul 2013 18:18:46 -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 72260 invoked by uid 99); 19 Jul 2013 18:18:46 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 19 Jul 2013 18:18:46 +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 gorla.patricia@gmail.com designates 209.85.223.169 as permitted sender) Received: from [209.85.223.169] (HELO mail-ie0-f169.google.com) (209.85.223.169) by apache.org (qpsmtpd/0.29) with ESMTP; Fri, 19 Jul 2013 18:18:41 +0000 Received: by mail-ie0-f169.google.com with SMTP id 10so10303962ied.0 for ; Fri, 19 Jul 2013 11:18:20 -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=aEEzGWMdqUwRDfcyYy3GxpeHx1ZSR2zKAvnAal2GgLI=; b=LUZOgyIyyNGN2O/J3C/GABCRCLHkHv7V+B7rl59tJfwFbjvQT0TpVHmoOP8sCcD3nU fBJ6ZFJ4M03BEz1MWZZjChFIC2RD1JNzZ1NmN0TbzvWbafIw2xB4OBnNvr3E02om6hsH 38hrML00pjiL95oag7YrC0eADb9yW0CuqB/PnU9hUUfaI/EolomUMjTJ2Mdip9Ji08/h zrhzTkST9hmSbkrkenP8Np5M5J54mkz5XNRVlMaejVSIwLChOs5Nk+pFCMMO4AxUXkkI i0/PKc/dyjza2mWnF1Ctjrf+01ytBw0F9/CRnD9RXIhcJrsx2A6xD57Lv6HwzrV15VJG TiMw== X-Received: by 10.42.43.202 with SMTP id y10mr11871264ice.28.1374257900180; Fri, 19 Jul 2013 11:18:20 -0700 (PDT) MIME-Version: 1.0 Received: by 10.50.176.136 with HTTP; Fri, 19 Jul 2013 11:17:50 -0700 (PDT) In-Reply-To: <57C7C3CBDCB04F45A57AEC4CB21C0CCD1DBDEEB0@mbx024-e1-nj-6.exch024.domain.local> References: <57C7C3CBDCB04F45A57AEC4CB21C0CCD1DBDEEB0@mbx024-e1-nj-6.exch024.domain.local> From: Patricia Gorla Date: Fri, 19 Jul 2013 14:17:50 -0400 Message-ID: Subject: Re: CPU Bound Writes To: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=bcaec51018e9f85e8e04e1e15963 X-Virus-Checked: Checked by ClamAV on apache.org --bcaec51018e9f85e8e04e1e15963 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Kanwar, This is because writes are appends to the commit log, which is stored on disk, not memory. The commit log is then flushed to the memtable (in memory), before being written to an sstable on disk. So, most of the actions in sending out a write are writing to disk. Also see: http://www.datastax.com/docs/1.2/dml/about_writes Patricia On Fri, Jul 19, 2013 at 1:05 PM, Kanwar Sangha wrote: > =93Insert-heavy workloads will actually be CPU-bound in Cassandra before > being memory-bound=94**** > > ** ** > > Can someone explain why the internals of why writes are CPU bound ?**** > > ** ** > > ** ** > --bcaec51018e9f85e8e04e1e15963 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
Kanwar,

This is because writes are appe= nds to the commit log, which is stored on disk, not memory. The commit log = is then flushed to the memtable (in memory), before being written to an sst= able on disk.

So, most of the actions in sending out a write are writ= ing to disk.


Pa= tricia


On Fri, Jul 19, 2013 at 1:05 PM, Kanwar = Sangha <kanwar@mavenir.com> wrote:

=93Insert-heavy workloads will = actually be CPU-bound in Cassandra before being memory-bound=94

=A0

Can someone explain why the int= ernals of why writes are CPU bound ?

=A0

=A0


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