From: Andreas Dilger Subject: Re: bigalloc and max file size Date: Mon, 31 Oct 2011 10:08:20 -0600 Message-ID: <422BEB28-76D0-4FD8-B7AE-130C9AAE10C0@dilger.ca> References: <51BECC2B-2EBC-4FCB-B708-8431F7CB6E0D@dilger.ca> <5846CEDC-A1ED-4BB4-8A3E-E726E696D3E9@mit.edu> <97D9C5CC-0F22-4BC7-BDFA-7781D33CA7F3@whamcloud.com> <4EACE2B7.9070402@coly.li> <4EAE6BD4.9080705@coly.li> <583E0040-4EFA-4EBC-A738-A8968BB9135C@mit.edu> Mime-Version: 1.0 (iPhone Mail 8L1) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Cc: "i@coly.li" , Theodore Tso , Andreas Dilger , linux-ext4 development , Alex Zhuravlev , Tao Ma , "hao.bigrat@gmail.com" To: Theodore Tso Return-path: Received: from shawmail.shawcable.com ([64.59.128.220]:27308 "EHLO mail.shawcable.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933054Ab1JaQH2 convert rfc822-to-8bit (ORCPT ); Mon, 31 Oct 2011 12:07:28 -0400 In-Reply-To: <583E0040-4EFA-4EBC-A738-A8968BB9135C@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 2011-10-31, at 4:22 AM, Theodore Tso wrote: > For cluster file systems, such as when you might build Hadoop on top of ext4, there's no real advantage of using RAID arrays as opposed to having single file systems on each disk. In fact, due to the specd of being able to check multiple disk spindles in parallel, it's advantageous to build cluster file systems on single disk file systems. For Lustre at least there are a number of reasons why it uses large RAID devices to store the data instead of many small devices: - fewer devices that need to be managed. Lustre runs on systems with more than 13000 drives, and having to manage connection state for that many internal devices is a lot of overhead.