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 EE609999B for ; Mon, 26 Mar 2012 17:48:13 +0000 (UTC) Received: (qmail 7049 invoked by uid 500); 26 Mar 2012 17:48:11 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 7020 invoked by uid 500); 26 Mar 2012 17:48:11 -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 7011 invoked by uid 99); 26 Mar 2012 17:48:11 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 26 Mar 2012 17:48:11 +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-a91.g.dreamhost.com) (208.113.200.5) by apache.org (qpsmtpd/0.29) with ESMTP; Mon, 26 Mar 2012 17:48:05 +0000 Received: from homiemail-a91.g.dreamhost.com (localhost [127.0.0.1]) by homiemail-a91.g.dreamhost.com (Postfix) with ESMTP id C2C99AE075 for ; Mon, 26 Mar 2012 10:47:43 -0700 (PDT) Received: from [172.16.1.3] (125-236-193-159.adsl.xtra.co.nz [125.236.193.159]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) (Authenticated sender: aaron@thelastpickle.com) by homiemail-a91.g.dreamhost.com (Postfix) with ESMTPSA id 2CA54AE072 for ; Mon, 26 Mar 2012 10:47:43 -0700 (PDT) From: aaron morton Mime-Version: 1.0 (Apple Message framework v1257) Content-Type: multipart/alternative; boundary="Apple-Mail=_6C3746A0-22D5-45EB-9144-5B5C45BB2D3B" Subject: Re: One or Two clusters? Date: Tue, 27 Mar 2012 06:47:39 +1300 In-Reply-To: <58E6BABE-FCB3-4FD7-BBF8-2A5BDF5C48BA@cloudorange.com> To: user@cassandra.apache.org References: <58E6BABE-FCB3-4FD7-BBF8-2A5BDF5C48BA@cloudorange.com> Message-Id: <6917B74E-564C-4964-86A4-ED20AD18FEC8@thelastpickle.com> X-Mailer: Apple Mail (2.1257) X-Virus-Checked: Checked by ClamAV on apache.org --Apple-Mail=_6C3746A0-22D5-45EB-9144-5B5C45BB2D3B Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Use one cluster. Use lots-o-machines. The read and write paths do not directly interfere with each other like = they do in a RDBMS. Compaction created by writes can suck up disk IO, = but this is throttled so in practice it is not such a big problem. = Excessive GC created by reads or compaction may slow down the server, = but you will want to avoid them anyway. The one caveat is: it depends on how you are transforming the data. If = you have a are using Hadoop consider creating a single cluster with = multiple DC's (like Data Stax do). One for OLTP and one for OLAP, do the = hadoop work in the OLAP DC and have the online app read-write to the = OLTP one.=20 Cheers ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 27/03/2012, at 3:22 AM, Oleg Proudnikov wrote: > Hi, >=20 > Could someone please help me understand the benefits of having a = single large cluster vs. having two smaller clusters separated by the = pattern of use? One, MOSTLY WRITE cluster could incrementally accumulate = large amounts of data throughout the day. The daily increment would be = processed, summarized and stored into the second READ cluster at night. = Users would only need to interact with the READ portion of the overall = system mostly during the day. Writes would be spread throughout the day = and will be a function of user activity with some bulk load activity = from time to time. WRITE portion of the database would be an order of = magnitude larger than the READ portion. READ portion would have an an = order of magnitude higher traffic except during periodic bulk loads. >=20 > On one hand, If I were to have a single cluster I would have more = resources for the users and potentially better scalability. A single = cluster may need fewer servers overall, provided write activity does not = affect reads... On the other hand, write activity and associated memory = consumption, GC, as well as maintenance riutines may affect READ system. = The system will be hosted on EC2. >=20 > I would appreciate any thoughts. >=20 > Regards, > Oleg --Apple-Mail=_6C3746A0-22D5-45EB-9144-5B5C45BB2D3B Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii Use = one cluster. Use lots-o-machines.

The read and write = paths do not directly  interfere with each other like they do = in a RDBMS. Compaction created by writes can suck up disk IO, but this = is throttled so in practice it is not such a big problem. Excessive GC = created by reads or compaction may slow down the server, but you will = want to avoid them anyway.

The one caveat is: = it depends on how you are transforming the data. If you have a are using = Hadoop consider creating a single cluster with multiple DC's (like Data = Stax do). One for OLTP and one for OLAP, do the hadoop work in the OLAP = DC and have the online app read-write to the OLTP = one. 

Cheers

http://www.thelastpickle.com

On 27/03/2012, at 3:22 AM, Oleg Proudnikov wrote:

Hi,

Could someone please help me understand = the benefits of having a single large cluster vs. having two smaller = clusters separated by the pattern of use? One, MOSTLY WRITE cluster = could incrementally accumulate large amounts of data throughout the day. = The daily increment would be processed, summarized and stored into the = second READ cluster at night. Users would only need to interact with the = READ portion of the overall system mostly during the day. Writes would = be spread throughout the day and will be a function of user activity = with some bulk load activity from time to time.  WRITE portion of = the database would be an order of magnitude larger than the READ = portion. READ portion would have an an order of magnitude higher traffic = except during periodic bulk loads.

On one hand, If I were to have = a single cluster I would have more  resources for the users and = potentially better scalability. A single cluster may need fewer servers = overall, provided write activity does not affect reads... On the other = hand, write activity and associated memory consumption, GC, as well as = maintenance riutines may affect READ system. The system will be hosted = on EC2.

I would appreciate any = thoughts.

Regards,
Oleg

= --Apple-Mail=_6C3746A0-22D5-45EB-9144-5B5C45BB2D3B--