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 6C10D1381F3 for ; Thu, 20 Jun 2013 19:10:13 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id E6024E09C0; Thu, 20 Jun 2013 19:10:06 +0000 (UTC) Received: from mail-pd0-f177.google.com (mail-pd0-f177.google.com [209.85.192.177]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 1F05AE0996 for ; Thu, 20 Jun 2013 19:10:05 +0000 (UTC) Received: by mail-pd0-f177.google.com with SMTP id p10so6505883pdj.22 for ; Thu, 20 Jun 2013 12:10:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=s41chLtLhSyDBreL1yPOEpPLqEw8ntnuYhsbYuUOdfY=; b=JntnCY/bTyqpbgj14twYyOf+32tH1b7rkg37TPRRpfxRM4LuzgetiPFJlVMEOtG6N/ mLoYZV8c9Qf8Ky6ZBSM9jHshmCJymGexRDjznzOinToJOIgcEoVcN/k6ZUTtZ5FgpgJZ MvVm43CKmvKPYCOuy5LrSIEJNpu6S6ukP0wQQKdyPumLlER4vML+pTRUAx4C+iky41zq fVZ96ToBnXcomn9dT3EA+qqc0D2EEPo6+6iOt6R17UdMlHSLv26l+E1wv+YygaCGjoW4 ChY+2XTLCEzBSDQe3+btSvnqaNEA0HWPbt8jEjf3HmHJQGRZUzCmMHQSkwRoV3SRzL2n GQbQ== Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-amd64@lists.gentoo.org Reply-to: gentoo-amd64@lists.gentoo.org MIME-Version: 1.0 X-Received: by 10.68.211.199 with SMTP id ne7mr8762063pbc.56.1371755404946; Thu, 20 Jun 2013 12:10:04 -0700 (PDT) Received: by 10.70.33.198 with HTTP; Thu, 20 Jun 2013 12:10:04 -0700 (PDT) Date: Thu, 20 Jun 2013 12:10:04 -0700 Message-ID: Subject: [gentoo-amd64] Is my RAID performance bad possibly due to starting sector value? From: Mark Knecht To: Gentoo AMD64 Content-Type: text/plain; charset=UTF-8 X-Archives-Salt: c864de62-c8dc-4b9d-aaf3-d72c877b9a82 X-Archives-Hash: c62582b17a3da3291ddba6b00338c328 Hi, Does anyone know of info on how the starting sector number might impact RAID performance under Gentoo? The drives are WD-500G RE3 drives shown here: http://www.amazon.com/Western-Digital-WD5002ABYS-3-5-inch-Enterprise/dp/B001EMZPD0/ref=cm_cr_pr_product_top These are NOT 4k sector sized drives. Specifically I'm a 5-drive RAID6 for about 1.45TB of storage. My benchmarking seems abysmal at around 40MB/S using dd copying large files. It's higher, around 80MB/S if the file being transferred is coming from an SSD, but even 80MB/S seems slow to me. I see a LOT of wait time in top. And my 'large file' copies might not be large enough as the machine has 24GB of DRAM and I've only been copying 21GB so it's possible some of that is cached. Then I looked again at how I partitioned the drives originally and see the starting sector of sector 3 as 8594775. I started wondering if something like 4K block sizes at the file system level might be getting munged across 16k chunk sizes in the RAID. Maybe the blocks are being torn apart in bad ways for performance? That led me down a bunch of rabbit holes and I haven't found any light yet. Looking for some thoughtful ideas from those more experienced in this area. Cheers, Mark