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 1197298C8 for ; Thu, 21 Feb 2013 05:52:45 +0000 (UTC) Received: (qmail 87221 invoked by uid 500); 21 Feb 2013 05:52:43 -0000 Delivered-To: apmail-cassandra-user-archive@cassandra.apache.org Received: (qmail 87002 invoked by uid 500); 21 Feb 2013 05:52:42 -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 86968 invoked by uid 99); 21 Feb 2013 05:52:41 -0000 Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 21 Feb 2013 05:52:41 +0000 X-ASF-Spam-Status: No, hits=2.9 required=5.0 tests=HTML_MESSAGE,RCVD_IN_DNSWL_NONE,SPF_NEUTRAL X-Spam-Check-By: apache.org Received-SPF: neutral (nike.apache.org: local policy) Received: from [206.225.165.118] (HELO HUB024-nj-3.exch024.serverdata.net) (206.225.165.118) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 21 Feb 2013 05:52:31 +0000 Received: from MBX024-E1-NJ-6.exch024.domain.local ([10.240.10.56]) by HUB024-NJ-3.exch024.domain.local ([10.240.10.36]) with mapi id 14.02.0318.001; Wed, 20 Feb 2013 21:52:07 -0800 From: Kanwar Sangha To: "user@cassandra.apache.org" Subject: Read IO Thread-Topic: Read IO Thread-Index: Ac4P86BoIFrRhmtgSG6lHLCiAs+p0w== Date: Thu, 21 Feb 2013 05:52:09 +0000 Message-ID: <57C7C3CBDCB04F45A57AEC4CB21C0CCD1DB32F50@mbx024-e1-nj-6.exch024.domain.local> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [76.184.245.196] Content-Type: multipart/alternative; boundary="_000_57C7C3CBDCB04F45A57AEC4CB21C0CCD1DB32F50mbx024e1nj6exch_" MIME-Version: 1.0 X-Virus-Checked: Checked by ClamAV on apache.org --_000_57C7C3CBDCB04F45A57AEC4CB21C0CCD1DB32F50mbx024e1nj6exch_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hi - Can someone explain the worst case IOPS for a read ? No key cache, No = row cache, sampling rate say 512. 1) Bloom filter will be checked to see existence of key (In RAM) 2) Index filer sample (IN RAM) will be checked to find approx. locatio= n in index file on disk 3) 1 IOPS to read the actual index file on disk (DISK) 4) 1 IOPS to get the data from the location in the sstable (DISK) Is this correct ? --_000_57C7C3CBDCB04F45A57AEC4CB21C0CCD1DB32F50mbx024e1nj6exch_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hi – Can someone explain = the worst case IOPS for a read ? No key cache, No row cache, sampling rate = say 512.

 

1) &nbs= p;    Bloom filter will be ch= ecked to see existence of key (In RAM)

2) &nbs= p;    Index filer sample (IN = RAM) will be checked to find approx. location in index file on disk

3) &nbs= p;    1 IOPS to read the actu= al index file on disk (DISK)

4) &nbs= p;    1 IOPS to get the data = from the location in the sstable (DISK)

 

Is this correct ?

 

 

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