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 E40A69251 for ; Wed, 23 May 2012 10:01:08 +0000 (UTC) Received: (qmail 46394 invoked by uid 500); 23 May 2012 10:01:06 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 46168 invoked by uid 500); 23 May 2012 10:01:06 -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 46156 invoked by uid 99); 23 May 2012 10:01:06 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 23 May 2012 10:01:06 +0000 X-ASF-Spam-Status: No, hits=2.2 required=5.0 tests=HTML_MESSAGE,RCVD_IN_DNSWL_NONE,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: local policy) Received: from [208.113.200.5] (HELO homiemail-a44.g.dreamhost.com) (208.113.200.5) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 23 May 2012 10:00:58 +0000 Received: from homiemail-a44.g.dreamhost.com (localhost [127.0.0.1]) by homiemail-a44.g.dreamhost.com (Postfix) with ESMTP id 98A1611805C for ; Wed, 23 May 2012 03:00:36 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; c=nofws; d=thelastpickle.com; h=from :mime-version:content-type:subject:date:in-reply-to:to :references:message-id; q=dns; s=thelastpickle.com; b=wjUq1w9A+c dC6CZLsOjAF9B0pGn4uwTuYaOo9+JorsMNhlHsMbuWa5up9pExxDdAQB1qvC2aEr kB0h+wm1vkUVMc7GLaiGJfmH1pDnp4VQsSkjdN1eC4sVE/uHx82Ed4sYOzVX4Mp9 7FHKHfUmyVc/fykFug2+Dyzhs3qj7huxY= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=thelastpickle.com; h=from :mime-version:content-type:subject:date:in-reply-to:to :references:message-id; s=thelastpickle.com; bh=iDzlSSPnnQfa8/Xo +uTCKilWWm4=; b=lc0AdvZJF2P8q26IM35kTLCon2npooUhBY2VTxTBbnBt5B6f atxqinsnGc+SOy0XvjxiUTnGUU4NSN/wIfWJ9OaAPDPZhh1An4o0TXnD627Y5t5x ARgY245WMSM91b595/bDt0SZ6f1Hx2PoZJc2Gh6jR3iVC59ifX+70mZwHbo= Received: from [172.16.1.4] (unknown [203.86.207.101]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) (Authenticated sender: aaron@thelastpickle.com) by homiemail-a44.g.dreamhost.com (Postfix) with ESMTPSA id 1C649118058 for ; Wed, 23 May 2012 03:00:35 -0700 (PDT) From: aaron morton Mime-Version: 1.0 (Apple Message framework v1257) Content-Type: multipart/alternative; boundary="Apple-Mail=_518AE886-908B-465E-8AE9-C9F6D5AFF784" Subject: Re: Replication factor Date: Wed, 23 May 2012 22:00:25 +1200 In-Reply-To: To: user@cassandra.apache.org References: Message-Id: <5465E653-8578-42EF-A849-360610DC11DB@thelastpickle.com> X-Mailer: Apple Mail (2.1257) --Apple-Mail=_518AE886-908B-465E-8AE9-C9F6D5AFF784 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 RF is normally adjusted to modify availability (see = http://thelastpickle.com/2011/06/13/Down-For-Me/) > for example, if I have 4 nodes cluster in one data center, how can = RF=3D2 vs RF=3D4 affect read performance? If consistency level is ONE, = looks reading does not need to go to another hop to get data if RF=3D4, = but it would do more work on read repair in the background. Read Repair does not run at CL ONE. When RF =3D=3D number of nodes, and you read at CL ONE you will always = be reading locally. But with a low consistency. If you read with QUORUM when RF =3D=3D number of nodes you will still = get some performance benefit from the data being read locally. Cheers ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 23/05/2012, at 9:34 AM, Daning Wang wrote: > Hello, >=20 > What is the pros and cons to choose different number of replication = factor in term of performance? if space is not a concern. >=20 > for example, if I have 4 nodes cluster in one data center, how can = RF=3D2 vs RF=3D4 affect read performance? If consistency level is ONE, = looks reading does not need to go to another hop to get data if RF=3D4, = but it would do more work on read repair in the background. >=20 > Can you share some insights about this? >=20 > Thanks in advance, >=20 > Daning=20 >=20 --Apple-Mail=_518AE886-908B-465E-8AE9-C9F6D5AFF784 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1 RF is = normally adjusted to modify availability (see http://thelastpi= ckle.com/2011/06/13/Down-For-Me/)

for example, if I have 4 nodes cluster in one data center, = how can RF=3D2 vs RF=3D4 affect read performance? If consistency level = is ONE, looks reading does not need to go to another hop to get data if = RF=3D4, but it would do more work on read repair in the = background.
Read Repair does not run at CL = ONE.
When RF =3D=3D number of nodes, and you read at CL ONE = you will always be reading locally. But with a low = consistency.
If you read with QUORUM when RF =3D=3D number of = nodes you will still get some performance benefit from the data being = read locally.

Cheers


http://www.thelastpickle.com

On 23/05/2012, at 9:34 AM, Daning Wang wrote:

Hello,

What is the pros and cons to choose = different number of replication factor in term of performance? if space = is not a concern.

for example, if I have 4 nodes cluster in one = data center, how can RF=3D2 vs RF=3D4 affect read performance? If = consistency level is ONE, looks reading does not need to go to another = hop to get data if RF=3D4, but it would do more work on read repair in = the background.

Can you share some insights about this?

Thanks in = advance,

Daning


= --Apple-Mail=_518AE886-908B-465E-8AE9-C9F6D5AFF784--