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 828EA9F88 for ; Thu, 16 Feb 2012 08:31:22 +0000 (UTC) Received: (qmail 33418 invoked by uid 500); 16 Feb 2012 08:31:20 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 33395 invoked by uid 500); 16 Feb 2012 08:31:20 -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 33387 invoked by uid 99); 16 Feb 2012 08:31:20 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 16 Feb 2012 08:31:20 +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 (nike.apache.org: local policy) Received: from [208.113.200.5] (HELO homiemail-a79.g.dreamhost.com) (208.113.200.5) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 16 Feb 2012 08:31:11 +0000 Received: from homiemail-a79.g.dreamhost.com (localhost [127.0.0.1]) by homiemail-a79.g.dreamhost.com (Postfix) with ESMTP id 833E37D406F for ; Thu, 16 Feb 2012 00:30:48 -0800 (PST) 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=yrhksXS8zV llxh4hmtdOw5PN2uDd2kM3UJiY/cLCzKUjfWVS8i8FEjmAjuCOhdq4/QnYZNsuLt Tpd6s4SY9P41/8BbZaeGb5bzzPTz+VPFpc03w5DhMyHtwjqnj28XOpmLzLA7wQS3 tWA6jS7Vb396HZse4OfrBazWkEKNYa0U4= 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=XYvhYJ+HNP0/ua9e 0qYs848bTSY=; b=MlrHXQlzkbVvOYKe2WbEGvEAh4p/fAQapq+1jyXiRbDcLPv4 T0cQtvaP+VGxK1dyux17a8s8qD42q4Q53yuLGMCNEfq3bsfmbYBhADHyQs7jAian bB0/b2vZSFRHwcrWEcgiUGV4hGa29nmwhwScRLEn9SWN/KECXYex2DI4c2s= 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-a79.g.dreamhost.com (Postfix) with ESMTPSA id D24467D4057 for ; Thu, 16 Feb 2012 00:30:47 -0800 (PST) From: aaron morton Mime-Version: 1.0 (Apple Message framework v1251.1) Content-Type: multipart/alternative; boundary="Apple-Mail=_82F84834-7CE8-42DF-B038-954B3AB01A76" Subject: Re: Key cache hit rate issue Date: Thu, 16 Feb 2012 21:30:44 +1300 In-Reply-To: To: user@cassandra.apache.org References: Message-Id: X-Mailer: Apple Mail (2.1251.1) X-Virus-Checked: Checked by ClamAV on apache.org --Apple-Mail=_82F84834-7CE8-42DF-B038-954B3AB01A76 Content-Transfer-Encoding: quoted-printable 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? Sorry I don't understand what you mean. But if the ratio is 0.0 all is = good.=20 Could you include the full output from cfstats for the CF you are = looking at ? Cheers ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 15/02/2012, at 1:00 PM, Eran Chinthaka Withana wrote: > 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? >=20 > Thanks, > Eran Chinthaka Withana >=20 >=20 > 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. >=20 >> Also, is there a way to warm start the key cache, meaning pre-load = the amount of keys I set as keys_cached? >=20 > See key_cache_save_period when creating the CF. >=20 > Cheers >=20 >=20 > ----------------- > Aaron Morton > Freelance Developer > @aaronmorton > http://www.thelastpickle.com >=20 > On 15/02/2012, at 5:54 AM, Eran Chinthaka Withana wrote: >=20 >> Hi, >>=20 >> 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? >>=20 >> Here is what I see on cfstats. >>=20 >> Key cache capacity: 16637958 >> Key cache size: 16637958 >> Key cache hit rate: 0.045454545454545456 >>=20 >> Also, is there a way to warm start the key cache, meaning pre-load = the amount of keys I set as keys_cached? >>=20 >> Thanks, >> Eran >=20 >=20 --Apple-Mail=_82F84834-7CE8-42DF-B038-954B3AB01A76 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; 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?
Sorry I don't understand what you mean. = But if the ratio is 0.0 all is = good. 

Could you include the full output = from cfstats for the CF you are looking at = ?

Cheers

http://www.thelastpickle.com

On 15/02/2012, at 1:00 PM, Eran Chinthaka Withana = wrote:

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 <aaron@thelastpickle.com> 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_sa= ve_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 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
=



= --Apple-Mail=_82F84834-7CE8-42DF-B038-954B3AB01A76--