From owner-freebsd-questions@FreeBSD.ORG Sat Jan 16 18:21:38 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B53FD1065676 for ; Sat, 16 Jan 2010 18:21:38 +0000 (UTC) (envelope-from dino_vliet@yahoo.com) Received: from web51105.mail.re2.yahoo.com (web51105.mail.re2.yahoo.com [206.190.38.147]) by mx1.freebsd.org (Postfix) with SMTP id 735588FC0A for ; Sat, 16 Jan 2010 18:21:38 +0000 (UTC) Received: (qmail 53562 invoked by uid 60001); 16 Jan 2010 18:21:35 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1263666095; bh=rk9PWyiLeGzpHnQMemJMkenTkVIvMkpHPju7PgH2D74=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type; b=pmpnJLekUSIx+yJ8f5oyqdEHYgt87eUueAfzUbiQLCN5a6tzCBDSs8kIRqKNDmb7Jv59YXVanKa9YuUza/5j7eFVjXLHSAfRcIFjhjLuvSMZXFxWcoR9ZEoZb5rmLzXFXtUWnD2tCuUADnqLM9mHM24bqPU3YPA2VJOV+olEKDo= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:Cc:MIME-Version:Content-Type; b=4lVb2WysD6QZsV6qeXkpInDLMnq7l9M/8z8B4ZZTxNrqQzg11fXHTNOxnem1NaTbJMS/8+Ud6EJ7ZFn+K+ttJQOM1W9dMJThBPvr6QMrsyc/TMVhOwFNS0sWQzWMJZrPLjkGCAPMcFPgqPqQjDeKKswUQi7g4aaQqTvKeon9pVo=; Message-ID: <178620.52606.qm@web51105.mail.re2.yahoo.com> X-YMail-OSG: g.v5DiYVM1l8AW0lwNI1zqMtac2PKxDln.zBSPFlx6eNjS4FbgsgxNxCBNOf0JJ6gD7tG8NvdyRXXzkP9J.YDVSFLW92AIm7j9PkOuWKmrBcZrmKgmMhChvOALqXcD3vQXbR510X.hTtSV7PTJrMKix7pgEHc01BWkNrm4JH_GqmymrSgLhyL1PK4lN1f9RNSX2lrPKyUs89Pl7xcinnFWNZTDAICR4i_hzqvqOD_KnNnJRTCF2yZvCX.bcUQ3dFfzGkPZgvhhBRu1SshWBdyarnCcyVecAnU6vZe4mEN6fiCpYBJ1kQLSkpxA9rT38YqDXE9b5Ki477uDkh19Qkk6Xesf9oC2xh Received: from [85.144.145.49] by web51105.mail.re2.yahoo.com via HTTP; Sat, 16 Jan 2010 10:21:35 PST X-Mailer: YahooMailClassic/9.0.20 YahooMailWebService/0.8.100.260964 Date: Sat, 16 Jan 2010 10:21:35 -0800 (PST) From: Dino Vliet To: jmc-freebsd2@milibyte.co.uk MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-questions@freebsd.org Subject: Newbie gmirror questions X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 16 Jan 2010 18:21:38 -0000 Forwarded Message: Newbie gmirror questions Newbie gmirror questions Saturday, January 16, 2010 12:34 AM From: "Mike Clarke" To: freebsd-questions@freebsd.org I'm about to upgrade to more disk space and I'm tempted use this as an opportunity to get two disks and implement gmirror. Before I go ahead there's a few aspects of mirroring I'm not sure about and would appreciate some advice. I'm using grub for multi booting. Does this introduce any problems if I want to boot into Windows or Linux on one of the other partitions? The gmirror manpage describes the procedure for handling kernel dumps using the prefer balance algorithm in the early stages of booting and then switching to round-robin in the /etc/rc.local script. It then goes on to say that "If on the next boot a component with a higher priority will be available, the prefer algorithm will choose to read from it and savecore(8) will find nothing". Does this only arise if I've made some change to the configuration of the mirror between the dump and the reboot or is there some instances when the priority automatically changes? Some of the articles I've read about gmirror suggest setting the balance to round-robin while others just leave this at the default setting of split. Am I right in assuming that round-robin would give better performance, and does it make much noticeable difference in real terms. In particular am I likely to see a reduction in performance using gmirror compared with what I would get with just a normal single disk. Finally, recent articles say to set kern.geom.debugflags to 17 when creating a mirror on a mounted drive while older articles say to set it to 16. Although I'll probably be creating the mirror on my disks before copying my system onto them so I don't really need to worry about setting this flag but I'm curious to know the difference between using the two values. -- Mike Clarke ****************** Hi Mike, I' ve just (ok, two weeks ago) completed a gmirror setup so can tell about what I know about this process However, my setup is not the same as yours because I' m not in a multi boot situation. I let others give their opinion regarding GRUB. I do guess that your OS-es are on a separate disk and in FreeBSD you will create a mirror with the two identical disks using gmirror. I've used round-robin because that's what the handbook suggested. I used kern.geom.debugflags = 17 because I looked at the handbook and guessed the other articles which suggested 16 were not up to date and it worked flawlessly. BrgdsDino