From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id D9405138E66 for ; Mon, 24 Feb 2014 17:05:02 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id 52CA7E0B34; Mon, 24 Feb 2014 17:04:55 +0000 (UTC) Received: from mail-ea0-f179.google.com (mail-ea0-f179.google.com [209.85.215.179]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 1FD87E0B1B for ; Mon, 24 Feb 2014 17:04:53 +0000 (UTC) Received: by mail-ea0-f179.google.com with SMTP id q10so3266731ead.24 for ; Mon, 24 Feb 2014 09:04:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type:content-transfer-encoding; bh=799blHhdosCfB/yb6o6QaUTNFQBvbQK379pkqWMuy7Y=; b=Cm0lc97NLKOajhimxuYRKmNho6msJhNQ7nyitf+0qzJPQUAwnlFTLGd5+J/uLnIvQn JHW5eUvRIolVUEL9IKb2KTVVwXjqK+O33xGLEjsNYsAyX8YfuqApi66H/zeoBFEzC8MU izlhQ7YWWJpoVGq2jdKRJxRkfGbKkJiLTSkJlLA/Ad89F+FFw8TmYydTychPopZHIkgI OR7qyrLq/rDDRZrNyqv3JM53gOO1P8hCDXkEA8X/J+XKmfTnLk7ghvIAXBbp93/HW8pf SksByijpXJ0VkQey9IaI2BvhfutmznemqIee7w1Iwxs03sQR6YOcE6mHYWfz7U88qyLZ kNiw== X-Received: by 10.15.111.130 with SMTP id cj2mr25474844eeb.102.1393261492736; Mon, 24 Feb 2014 09:04:52 -0800 (PST) Received: from [10.0.0.11] ([88.151.79.120]) by mx.google.com with ESMTPSA id x6sm65976391eew.20.2014.02.24.09.04.50 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 24 Feb 2014 09:04:52 -0800 (PST) Message-ID: <530B7B72.8040205@gmail.com> Date: Mon, 24 Feb 2014 18:03:46 +0100 From: Jarry User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] RAID 1 vs RAID 0 - Read perfonmance References: In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Archives-Salt: efc9822b-07d7-4496-97a0-0805c11fb229 X-Archives-Hash: fb6dcf843d4b25e238e659a15ac5b382 On 24-Feb-14 7:27, Facundo Curti wrote: > n= number of disks > > reads: > raid1: n*2 > raid0: n*2 > > writes: > raid1: n > raid0: n*2 > > But, in real life, the reads from raid 0 doesn't work at all, because if > you use "chunk size" from 4k, and you need to read just 2kb (most binary > files, txt files, etc..). the read speed should be just of n. Definitely not true. Very rarely you need to read just one small file. Mostly you need many small files (i.e. compilation) or a few big files (i.e. database). I do not know what load you expect, but in my case raid0 (with SSD) gave me about twice the r/w speed on heavily-loaded virtualization platform with many virtual machines. And not only speed is higher, but also IOPS are splitted to two disks (nearly doubled). I did some testing with 2xSSD/512GB in raid1, 2xSSD/256GB in raid0 and 3xSSD/256GB in raid5 (I used 840/pro SSD with quite good HW-controller but I think with mdadm it might be similar). Raid0 was way ahead of other two configurations in my case. Finally I went for 4xSSD/256GB in raid10 as I needed both speed and redundancy... Jarry -- _______________________________________________________________ This mailbox accepts e-mails only from selected mailing-lists! Everything else is considered to be spam and therefore deleted.