Return-Path: Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: (qmail 87238 invoked from network); 3 Apr 2011 19:36:05 -0000 Received: from hermes.apache.org (HELO mail.apache.org) (140.211.11.3) by minotaur.apache.org with SMTP; 3 Apr 2011 19:36:05 -0000 Received: (qmail 90525 invoked by uid 500); 3 Apr 2011 19:36:03 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 90493 invoked by uid 500); 3 Apr 2011 19:36:03 -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 90485 invoked by uid 99); 3 Apr 2011 19:36:03 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Sun, 03 Apr 2011 19:36:03 +0000 X-ASF-Spam-Status: No, hits=1.5 required=5.0 tests=FREEMAIL_FROM,HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (athena.apache.org: domain of anurag.gujral@gmail.com designates 209.85.160.44 as permitted sender) Received: from [209.85.160.44] (HELO mail-pw0-f44.google.com) (209.85.160.44) by apache.org (qpsmtpd/0.29) with ESMTP; Sun, 03 Apr 2011 19:35:57 +0000 Received: by pwi5 with SMTP id 5so1457705pwi.31 for ; Sun, 03 Apr 2011 12:35:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=WyT32NqmZ/tHitKuwcXtGeV5HgZFd9oq2kuvV4LJl1c=; b=RMaASq1003F0WambrfKdrXYW/SLFYR02A7He3neMDmwiRIWdQTNVDujiWZ/JLWiX4A 9680VKnjwBJgZyk208UfiyC45iSXl78KyzDvW6VAMGgr5y15xsma/Qa4csyEx6JG6LEL lnaT2gQb2Dq/f7O3n/huticrYVqGsEqYCSSM4= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=K7kJEdCgRrUYQw+ABlCiIklmonKo2IodmHPppR9AraJJeqBZyHlknEVfbwTLSML+Nq 6mv81tZB0OHtgGTZN3D4/bZeQukClRtEfZ5FXkvmOVICk9kyBspskNHLstQagl9phZOT eEblV0NY9EO1N7zcm0h+SQ6BcZnIsjCHfpRFY= MIME-Version: 1.0 Received: by 10.142.43.16 with SMTP id q16mr5316804wfq.364.1301859337151; Sun, 03 Apr 2011 12:35:37 -0700 (PDT) Received: by 10.68.56.227 with HTTP; Sun, 3 Apr 2011 12:35:37 -0700 (PDT) In-Reply-To: References: Date: Sun, 3 Apr 2011 12:35:37 -0700 Message-ID: Subject: Re: compaction behaviour From: Anurag Gujral To: Zhu Han Cc: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=000e0cd1a16456a55604a008bf51 --000e0cd1a16456a55604a008bf51 Content-Type: text/plain; charset=ISO-8859-1 Hi Zhu, I did not got that SSDs have read latency of 0.1ms.Since there is only one data file I would expect the read of any key to take 0.1ms may be I am missing something please explain. Thanks Anurag On Sun, Apr 3, 2011 at 5:01 AM, Zhu Han wrote: > > best regards, > Zhu Han > > > > On Sun, Apr 3, 2011 at 9:21 AM, Anurag Gujral wrote: > >> Hi All, >> I have loaded data into cassandra using batch processing the >> response times for reads are in the range of 0.8 ms but I am using SSDs. so >> I expect the read times to be even faster. >> > > Does your working set fit in the memory? If so, SSD is not helpful to > reduce the latency. > > >> Every time I run compaction the latency numbers reduce to 0.3 to 0.4ms , >> is there a way I can run compaction once with some parameters >> so that i can get the same numbers 0.3 to 0.4 ms for reads. >> Please note that I am not loading the data again. >> >> Thanks >> Anurag >> > > --000e0cd1a16456a55604a008bf51 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hi Zhu,
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 I did not got that SSDs=A0 = have read latency of 0.1ms.Since there is only one data file
I would exp= ect the read of any key to take 0.1ms may be I am missing something
plea= se explain.
Thanks
Anurag

On Sun, Apr 3, 2011 at 5:01 AM, Zh= u Han <schumi.= han@gmail.com> wrote:

best regards,
Zhu Han



On Sun, Apr 3, 2011 at= 9:21 AM, Anurag Gujral <anurag.gujral@gmail.com> wrot= e:
Hi All,
=A0=A0 =A0 =A0 =A0 =A0 I have loaded data into cassandra using = batch processing =A0the response times for reads are in the range of =A00.8= ms but I am using SSDs.=A0so I expect the read times to be even faster.

Does your working set fit in the memory? If so, SSD is not h= elpful to reduce the latency.
=A0
Every time I run compaction the latency numbers reduce to 0.3 to 0.4ms= =A0, is there a way I can run compaction once with some parameters=A0
so that i can get the same numbers 0.3 to 0.4 ms for reads.
= Please note that I am not loading the data again.

= Thanks
Anurag


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