From owner-freebsd-questions@freebsd.org Thu Oct 22 14:11:19 2015 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 13F60A1C394 for ; Thu, 22 Oct 2015 14:11:19 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-wi0-x22d.google.com (mail-wi0-x22d.google.com [IPv6:2a00:1450:400c:c05::22d]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id AEAB01158 for ; Thu, 22 Oct 2015 14:11:18 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: by wicfx6 with SMTP id fx6so137668323wic.1 for ; Thu, 22 Oct 2015 07:11:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20120113; h=date:from:to:subject:message-id:in-reply-to:references:mime-version :content-type:content-transfer-encoding; bh=FeSO7YohSfs5m0P7E18VsS9z4s6lK6wBYKiVlLnE6D8=; b=lgAIWlnurgN7sRiNwSDDKyYi5jNajMONFvE0CceEcopq75HpVthN9YHeCT2Egf7AZx EvHL/mCFJfd64/ieDDwlfdrocnN9BQ+EoqFg/pSJ0f1QtBGfcYINpd0TfZ3gOsPSXfSD j4WD1WEk/fTINaEozK4kLhiN7WQvMar6wIn9QJTxomNuJZz9Ph27Uc9poNYIkwMX2v0L 3t4SL9hvtIfn7if5JIr7jYELFxKjNdRXVoLYctJXyqpkEmrp1bggjcrC0mPZ4SC3GUde OIxqB0su5tVr5Mtm6zSZ12b/k2bzF8jTUX6zcLTBQkEnlgjA4zslcSBtT1dZ0Lrv18f7 DANQ== X-Received: by 10.180.90.37 with SMTP id bt5mr41124680wib.7.1445523077184; Thu, 22 Oct 2015 07:11:17 -0700 (PDT) Received: from gumby.homeunix.com ([90.195.214.153]) by smtp.gmail.com with ESMTPSA id lb10sm17104610wjc.9.2015.10.22.07.11.15 for (version=TLSv1/SSLv3 cipher=OTHER); Thu, 22 Oct 2015 07:11:16 -0700 (PDT) Date: Thu, 22 Oct 2015 15:11:15 +0100 From: RW To: freebsd-questions@freebsd.org Subject: Re: gjournal and TRIM: A safe combination? Message-ID: <20151022151115.33ee33f0@gumby.homeunix.com> In-Reply-To: <867fmh12nq.fsf@WorkBox.Home> References: <867fmh12nq.fsf@WorkBox.Home> X-Mailer: Claws Mail 3.13.0 (GTK+ 2.24.28; amd64-portbld-freebsd10.2) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 22 Oct 2015 14:11:19 -0000 On Tue, 20 Oct 2015 19:33:13 -0500 Brandon J. Wandersee wrote: > I've recently created several new UFS partitions on an SSD. I > activated gjournal on the largest--about 200Gb in size > 1. UFS with TRIM, but without journaling. Disk performance is > maintained, but data is unprotected in the event of a crash. UFS with soft-updates is roughly equivalent to the the metadata journalling used on most modern filesystems. Personally, I wouldn't use gjournal on an SSD for several reasons: 1. full data journalling doubles the writes with respect to basic UFS and therefore halves the life of the device. SU by contrast presumably reduces the total writes by rolling-up multiple metadata updates in memory. 2. the journal needs to be much larger than on an ordinary hard drive because of the write speeds, which is wasteful. 3. I suspect gjournal has had very little use on SSDs, so there may be SSD specific bugs. I use gjournal with large partitions on spinning disks, and soft-updates with foreground checks for my SSD and small partitions. I've never had a problem with SUs with foreground checks.