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 DA1129A26 for ; Wed, 15 Feb 2012 00:01:01 +0000 (UTC) Received: (qmail 54150 invoked by uid 500); 15 Feb 2012 00:00:59 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 54121 invoked by uid 500); 15 Feb 2012 00:00:59 -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 54113 invoked by uid 99); 15 Feb 2012 00:00:59 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 15 Feb 2012 00:00:59 +0000 X-ASF-Spam-Status: No, hits=1.5 required=5.0 tests=HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_PASS X-Spam-Check-By: apache.org Received-SPF: pass (nike.apache.org: domain of eran.chinthaka@gmail.com designates 209.85.214.172 as permitted sender) Received: from [209.85.214.172] (HELO mail-tul01m020-f172.google.com) (209.85.214.172) by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 15 Feb 2012 00:00:52 +0000 Received: by obbwd15 with SMTP id wd15so703463obb.31 for ; Tue, 14 Feb 2012 16:00:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=FR0ENDMH0E6QTi8H7vFawGVLtnHvMiZTHzFfkXbUxOk=; b=nOdkjB4x+l2uyIiBBMW/67A7V89RSk60kniQb3fyrrXuZYFkRKgG7A8ZPs1hIE85JA 5CvnsT7abAcNAiZor4cnQB8nrpABS5gTpWYGWXgFfNBcvjT2zNaG1h4+2CFPL1fQx5d0 9udV95i8pxMmCPuFR+k7nGMBcG2xtr9GT8Lko= MIME-Version: 1.0 Received: by 10.60.18.163 with SMTP id x3mr1808361oed.10.1329264031264; Tue, 14 Feb 2012 16:00:31 -0800 (PST) Received: by 10.60.1.168 with HTTP; Tue, 14 Feb 2012 16:00:31 -0800 (PST) In-Reply-To: References: Date: Tue, 14 Feb 2012 16:00:31 -0800 Message-ID: Subject: Re: Key cache hit rate issue From: Eran Chinthaka Withana To: user@cassandra.apache.org Content-Type: multipart/alternative; boundary=e89a8f923fba656dd104b8f5663c X-Virus-Checked: Checked by ClamAV on apache.org --e89a8f923fba656dd104b8f5663c Content-Type: text/plain; charset=ISO-8859-1 Its in the order of 261 to 8000 and the ratio is 0.00. But i guess 8000 is bit high. Is there a way to fix/improve it? Thanks, Eran Chinthaka Withana On Tue, Feb 14, 2012 at 3:42 PM, aaron morton wrote: > Out of interest what does cfstats say about the bloom filter stats ? A > high false positive could lead to a low key cache hit rate. > > Also, is there a way to warm start the key cache, meaning pre-load the > amount of keys I set as keys_cached? > > See key_cache_save_period when creating the CF. > > Cheers > > > ----------------- > Aaron Morton > Freelance Developer > @aaronmorton > http://www.thelastpickle.com > > On 15/02/2012, at 5:54 AM, Eran Chinthaka Withana wrote: > > Hi, > > I'm using Cassandra 1.0.7 and I've set the keys_cached to about 80% (using > the numerical values). This is visible in cfstats too. But I'm getting less > than 20% (or sometimes even 0%) key cache hit rate. Well, the data access > pattern is not the issue here as I know they are retrieving the same row > multiple times. I'm using hector client with dynamic load balancing policy > with consistency ONE for both reads and writes. Any ideas on how to find > the issue and fix this? > > Here is what I see on cfstats. > > Key cache capacity: 16637958 > Key cache size: 16637958 > Key cache hit rate: 0.045454545454545456 > > Also, is there a way to warm start the key cache, meaning pre-load the > amount of keys I set as keys_cached? > > Thanks, > Eran > > > --e89a8f923fba656dd104b8f5663c Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Its in the order of 261 to 8000 and the ratio is 0.00. But i guess 8000 is = bit high. Is there a way to fix/improve it?

Thanks,Eran Chinthaka Withana


On Tue, Feb 14, 2012 at 3:42 PM, aaron m= orton <aaro= n@thelastpickle.com> wrote:
Out of interest what does cfstats = say about the bloom filter stats ? A high false positive could lead to a lo= w key cache hit rate.

Also, is there a way to warm start the key cache, meaning pre-load the= amount of keys I set as keys_cached?
See=A0key_cache_save_period when creating the CF.

Cheers


-----------------
Aaron Morton
Freelance Developer
@aaronmorton

On 15/02/2012, at 5:54 AM, Eran Chinthaka Withana wrote:
Hi,

I'm using Cassand= ra 1.0.7 and I've set the keys_cached to about 80% (using the numerical= values). This is visible in cfstats too. But I'm getting less than 20%= (or sometimes even 0%) key cache hit rate. Well, the data access pattern i= s not the issue here as I know they are retrieving the same row multiple ti= mes. I'm using hector client with dynamic load balancing policy with co= nsistency ONE for both reads and writes. Any ideas on how to find the issue= and fix this?

Here is what I see on cfstats.

Key cache capacity: 16637958
Key cache size: 16637958
=
Key cache hit rate: 0.045454545454545456

Also, is there a way to warm start the key cache, meaning pre-load the= amount of keys I set as keys_cached?

Thanks,
Eran


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