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 B61DBCA07 for ; Thu, 24 May 2012 09:55:23 +0000 (UTC) Received: (qmail 12562 invoked by uid 500); 24 May 2012 09:55:20 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 12507 invoked by uid 500); 24 May 2012 09:55:20 -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 12284 invoked by uid 99); 24 May 2012 09:55:20 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 24 May 2012 09:55:20 +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 (athena.apache.org: local policy) Received: from [208.113.200.5] (HELO homiemail-a94.g.dreamhost.com) (208.113.200.5) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 24 May 2012 09:55:15 +0000 Received: from homiemail-a94.g.dreamhost.com (localhost [127.0.0.1]) by homiemail-a94.g.dreamhost.com (Postfix) with ESMTP id 605BD38A059 for ; Thu, 24 May 2012 02:54:54 -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=le7aG+mBK5 HyYVeAxGxA4yU/JOhNU/GcSd81TbTLY9uuF0LJ53vcF23/eRzhJ0QyCzM7cQ3hOb ZjSOpE/au0hzmwuirIHun+mV2SLhHIpAKZHXFSYVjPr0KpOc1zotLpZSCK/APqLx 8ToUBbWOIhAuwdofZB+qfp+SfKIPq464s= 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=F/3l8N/7LH4hDcmU y+x/5v2O5I4=; b=r0SQIHoP2vS4NKONRNB9VtqIToR5yRoHHQtOfNh3umYMriTI U1LWR35ZDDPams8tYtn78pyQ3hjI1U9FJfrCuLe4hobt+oWzKMZB1et/g5QgU1GS 1o1ULUx+CoVLVRe44hGgbWR8p+qdztN56lxd64MWjeVVSWXS5NELm1dh64Y= 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-a94.g.dreamhost.com (Postfix) with ESMTPSA id A1A8738A00C for ; Thu, 24 May 2012 02:54:53 -0700 (PDT) From: aaron morton Mime-Version: 1.0 (Apple Message framework v1257) Content-Type: multipart/alternative; boundary="Apple-Mail=_915156A2-787B-4DBE-B97B-9E970BCE635B" Subject: Re: Replication factor Date: Thu, 24 May 2012 21:54:49 +1200 In-Reply-To: To: user@cassandra.apache.org References: <5465E653-8578-42EF-A849-360610DC11DB@thelastpickle.com> <2C85E14562B39345BCCAD90B8E7955C913E4B4@DKEXC002.adform.com> Message-Id: X-Mailer: Apple Mail (2.1257) X-Virus-Checked: Checked by ClamAV on apache.org --Apple-Mail=_915156A2-787B-4DBE-B97B-9E970BCE635B Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 ReadRepair means including all UP replicas in the request, waiting = asynchronously after the read has completed, resolving and repairing = differences. If you read at QUOURM with RR running, ALL (replace) nodes = will perform a read.=20 At any CL > ONE the responses from CL nodes are reconciled and = differences are repaired using a mechanism similar to RR. This has to = happen before the response can be sent to the client. The naming does not help, but they are a different. RR is a background = process designed to reduce the chance of an inconsistent read. It's = needed less since changed to Hinted Handoff in 1.0. Cheers =20 ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 24/05/2012, at 5:47 AM, Daning Wang wrote: > Thanks guys. >=20 > Aaron, I am confused about this. from wiki = http://wiki.apache.org/cassandra/ReadRepair, looks for any consistency = level. Read Repair will be done either before or after responding data. >=20 > >Read Repair does not run at CL ONE >=20 > Daning >=20 > On Wed, May 23, 2012 at 3:51 AM, Viktor Jevdokimov = wrote: > > When RF =3D=3D number of nodes, and you read at CL ONE you will = always be reading locally. >=20 > =93always be reading locally=94 =96 only if Dynamic Snitch is =93off=94.= With dynamic snitch =93on=94 request may be redirected to other node, = which may introduce latency spikes. >=20 > =20 >=20 > =20 >=20 >=20 >=20 > Best regards / Pagarbiai > Viktor Jevdokimov > Senior Developer >=20 > Email: Viktor.Jevdokimov@adform.com > Phone: +370 5 212 3063, Fax +370 5 261 0453 > J. Jasinskio 16C, LT-01112 Vilnius, Lithuania > Follow us on Twitter: @adforminsider > What is Adform: watch this short video > =20 >=20 > Disclaimer: The information contained in this message and attachments = is intended solely for the attention and use of the named addressee and = may be confidential. If you are not the intended recipient, you are = reminded that the information remains the property of the sender. You = must not use, disclose, distribute, copy, print or rely on this e-mail. = If you have received this message in error, please contact the sender = immediately and irrevocably delete this message and any copies. >=20 > From: aaron morton [mailto:aaron@thelastpickle.com]=20 > Sent: Wednesday, May 23, 2012 13:00 > To: user@cassandra.apache.org > Subject: Re: Replication factor >=20 > =20 >=20 > RF is normally adjusted to modify availability (see = http://thelastpickle.com/2011/06/13/Down-For-Me/) >=20 > =20 >=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 > Read Repair does not run at CL ONE. >=20 > When RF =3D=3D number of nodes, and you read at CL ONE you will always = be reading locally. But with a low consistency. >=20 > 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. >=20 > =20 >=20 > Cheers >=20 > =20 >=20 > =20 >=20 > ----------------- >=20 > Aaron Morton >=20 > Freelance Developer >=20 > @aaronmorton >=20 > http://www.thelastpickle.com >=20 > =20 >=20 > On 23/05/2012, at 9:34 AM, Daning Wang wrote: >=20 >=20 >=20 >=20 > 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 >=20 >=20 --Apple-Mail=_915156A2-787B-4DBE-B97B-9E970BCE635B Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252
http://www.thelastpickle.com
On 24/05/2012, at 5:47 AM, Daning Wang wrote:

Thanks = guys.

Aaron, I am confused about this. from = wiki http://wiki.apache.or= g/cassandra/ReadRepair, looks for any consistency level. Read Repair = will be done either before or after responding data.

  >Read Repair does not run = at CL ONE

Daning

On Wed, = May 23, 2012 at 3:51 AM, Viktor Jevdokimov <Viktor.Jevdokimov@adform.com> wrote:

> When RF =3D=3D number = of nodes, and you read at CL ONE you will always be reading = locally.

=93always be reading locally=94 =96 only if = Dynamic Snitch is =93off=94. With dynamic snitch =93on=94 request may be = redirected to other node, which may introduce latency spikes.

 

 



Best regards / Pagarbiai
Viktor Jevdokimov
Senior Developer

J. Jasinskio 16C, LT-01112 Vilnius, Lithuania
Follow us on Twitter: @adforminsider

Disclaimer: The information contained in this message and attachments is = intended solely for the attention and use of the named addressee and may = be confidential. If you are not the intended recipient, you are reminded = that the information remains the property of the sender. You must not use, disclose, distribute, copy, print or = rely on this e-mail. If you have received this message in error, please = contact the sender immediately and irrevocably delete this message and = any copies.

From: aaron morton [mailto:aaron@thelastpickle.com]
Sent: Wednesday, May 23, 2012 13:00
To: user@cassandra.apache.org
Subject: Re: Replication factor

 

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

 

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=_915156A2-787B-4DBE-B97B-9E970BCE635B--