Return-Path: Delivered-To: apmail-cassandra-user-archive@www.apache.org Received: (qmail 51114 invoked from network); 15 Mar 2011 18:20:22 -0000 Received: from hermes.apache.org (HELO mail.apache.org) (140.211.11.3) by minotaur.apache.org with SMTP; 15 Mar 2011 18:20:22 -0000 Received: (qmail 86367 invoked by uid 500); 15 Mar 2011 18:20:19 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 86335 invoked by uid 500); 15 Mar 2011 18:20:19 -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 86327 invoked by uid 99); 15 Mar 2011 18:20:19 -0000 Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 15 Mar 2011 18:20:19 +0000 X-ASF-Spam-Status: No, hits=-0.0 required=5.0 tests=RCVD_IN_DNSWL_LOW,SPF_NEUTRAL X-Spam-Check-By: apache.org Received-SPF: neutral (athena.apache.org: local policy) Received: from [209.85.160.172] (HELO mail-gy0-f172.google.com) (209.85.160.172) by apache.org (qpsmtpd/0.29) with ESMTP; Tue, 15 Mar 2011 18:20:12 +0000 Received: by gyf3 with SMTP id 3so422748gyf.31 for ; Tue, 15 Mar 2011 11:19:50 -0700 (PDT) MIME-Version: 1.0 Received: by 10.151.32.1 with SMTP id k1mr326859ybj.385.1300213190012; Tue, 15 Mar 2011 11:19:50 -0700 (PDT) Sender: scode@scode.org Received: by 10.151.79.11 with HTTP; Tue, 15 Mar 2011 11:19:49 -0700 (PDT) X-Originating-IP: [90.232.2.178] In-Reply-To: References: Date: Tue, 15 Mar 2011 19:19:49 +0100 X-Google-Sender-Auth: TpX_Fl6B2Rfe1cotD3LfPeEJtqU Message-ID: Subject: Re: Calculate memory used for keycache From: Peter Schuller To: user@cassandra.apache.org Cc: Jean-Yves LEBLEU Content-Type: text/plain; charset=UTF-8 > One additionnal question, I don't really understand what is in the key > cache. I have a column family with only one key, and the keycache size > is 118 ... ? The key cache is basically a hash table mapping row keys to sstable offsets. It avoids the need to read from the index portion of the sstable for specific keys that have recently been accessed. (Normally the index portion is seeked into, a bit of data is streamed from disk, de-serialized, and used to find the offset for that key). -- / Peter Schuller