From owner-freebsd-questions@FreeBSD.ORG Thu Jan 28 16:51:25 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 C7307106566B for ; Thu, 28 Jan 2010 16:51:25 +0000 (UTC) (envelope-from amvandemore@gmail.com) Received: from mail-pw0-f44.google.com (mail-pw0-f44.google.com [209.85.160.44]) by mx1.freebsd.org (Postfix) with ESMTP id 9CAB68FC0C for ; Thu, 28 Jan 2010 16:51:25 +0000 (UTC) Received: by pwi15 with SMTP id 15so640987pwi.3 for ; Thu, 28 Jan 2010 08:51:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type; bh=Wz4s2hgvPUMKhBy7M6efe+P2FcCzTbV+bTkVVtpH0js=; b=i44nG78pdrYcH4DsvOP46eL+h4w9QnFuiPyUMGgY0Q0jicvENSgziqtpq2N/8RlSAM Psp7CHy8KT5ZSyj740LuFhM9Gb/NvqSGB2YEHj/OB8aVJC3hqioonX+zOzG/GK/C6LHQ XT4su/jaxZ2qdEWtngXAhN7MDuGjvS/jev3sg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=XFLovKnu93rNAL1vT9WOIXsxEMk9l5Z0J5XdOo2IPB12y/3kXb/fzONMBKsCUN71JO 6sTob6xdBbaaPh1EaKv8DQnTRoagkcnCmwp3bmrm3I6T1m8MPV/TT616vJ6sVNxB/l0k 4miTGdSMwR9PgJWWWJu7ksffL0FOjk0pPqiAk= MIME-Version: 1.0 Received: by 10.142.55.6 with SMTP id d6mr2508251wfa.303.1264697484996; Thu, 28 Jan 2010 08:51:24 -0800 (PST) In-Reply-To: <4B61BE70.1090109@gmx.com> References: <4B61BE70.1090109@gmx.com> Date: Thu, 28 Jan 2010 10:51:24 -0600 Message-ID: <6201873e1001280851i726f7827p520f138ee84217d8@mail.gmail.com> From: Adam Vande More To: Nikos Vassiliadis Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: "freebsd-questions@FreeBSD.org" Subject: Re: gjournal on compact flash 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: Thu, 28 Jan 2010 16:51:25 -0000 On Thu, Jan 28, 2010 at 10:42 AM, Nikos Vassiliadis wrote: > Hi, > > I am using a 40MB journal on a 500MB compact flash. > Would that be sane, or I am causing more harm than > good? > > My concerns are: > 1) wear leveling. The journal is on specific part > of the "disk" writing again and again. That > should be handled by the CF itself. Though > I am not sure it does a good job??? > 2) I do care about ungraceful power cycles and I've seen > posts on the net, mentioning: > >> More, If >> you interrupt power at arbitrary times while the device is writing, >> you can lose the integrity of the file system being modified. The loss >> is not limited to the 512 byte sector being modified, as it generally >> is with rotating disks; you can lose an entire erase block, maybe 64K >> at once. >> > I guess the above comment renders the use > of a journaling filesystem useless. But, doing > some naive tests, power cycling the machine > while writing and checksumming the data after > fsck in preen mode, revealed no error. > > Thanks in advance for any insights, Nikos > Soft Updates seem more appropriate for a 500MB CF drive than gjournal. AFAIK, they are a wash in terms of reliability, and gjournal needs to write all data twice meaning it's slower, and increases the wear on the drive. The big drawback to soft updates is the fsck times after an unclean shutdown which really shouldn't be an issue on a 500MB drive. -- Adam Vande More