Return-Path: Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: (qmail 46062 invoked from network); 13 Apr 2010 19:22:31 -0000 Received: from unknown (HELO mail.apache.org) (140.211.11.3) by 140.211.11.9 with SMTP; 13 Apr 2010 19:22:31 -0000 Received: (qmail 45321 invoked by uid 500); 13 Apr 2010 19:22:30 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 45302 invoked by uid 500); 13 Apr 2010 19:22:30 -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 45294 invoked by uid 99); 13 Apr 2010 19:22:30 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 13 Apr 2010 19:22:30 +0000 X-ASF-Spam-Status: No, hits=0.0 required=10.0 tests=FREEMAIL_FROM,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: domain of prescod@gmail.com designates 74.125.83.44 as permitted sender) Received: from [74.125.83.44] (HELO mail-gw0-f44.google.com) (74.125.83.44) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 13 Apr 2010 19:22:23 +0000 Received: by gwb1 with SMTP id 1so1981012gwb.31 for ; Tue, 13 Apr 2010 12:22:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:from:date:x-google-sender-auth:received:message-id :subject:to:cc:content-type:content-transfer-encoding; bh=pH2daVCSpXMgXPRRtEoqIVp1lrxDdLBvJolh8iG/Ujw=; b=aL0pw4XgvTq9RCoqTUNtznm/GKeadZHEOkkKO0GttsizDytHYOd88YPlEawMeUkp6m RiOBluDSRTRSGvfehJag+KrMugRC0Q1GodZcxHBH06TXglS/I6Pdgnvt7+fHTL6N+Vwb teVby51e8EcqqkvDqY+KOqcysOK4tBz5+pUqk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type :content-transfer-encoding; b=UO1Pz/dInHsd1ypJxETzfR4SYp7ZCeP2j3pFJJ1j3kVvbrSTIkZk3SvbiVO4WxpYct XGiWyO3aOz5kSxcS1s6cmwAoEiM4a+xOmoDlQ5tRHcaHt9O3qT4/9nHUQwvAiAEoPV7e yym9+Xh3Giim25vJMuWls9C/7U1GnrI2phMPo= MIME-Version: 1.0 Sender: prescod@gmail.com Received: by 10.100.231.17 with HTTP; Tue, 13 Apr 2010 12:21:40 -0700 (PDT) In-Reply-To: References: <61401.54585.qm@web111713.mail.gq1.yahoo.com> From: Paul Prescod Date: Tue, 13 Apr 2010 12:21:40 -0700 X-Google-Sender-Auth: 77040aa51495ebbb Received: by 10.101.211.36 with SMTP id n36mr10980774anq.120.1271186522458; Tue, 13 Apr 2010 12:22:02 -0700 (PDT) Message-ID: Subject: Re: Worst case #iops to read a row To: Benjamin Black Cc: user@cassandra.apache.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Virus-Checked: Checked by ClamAV on apache.org On Tue, Apr 13, 2010 at 12:00 PM, Benjamin Black wrote: >> I am probably being totally naive, but is the answer to the question >> "worst iops on read" just: >> >> =C2=A03 reads per SSTable * 4 SStables * ReplicationFactor ? >> >> =3D 3 * 4 * 3 =3D 36? >> > > Why does RF enter this? A simplistic model for a consistent read that is asking all replicas what their value is for the key. If the key is in the fourth SSTable of all nodes, won't they all have to do 12 IOPs to find it? Paul Prescod