From nobody Tue Aug 02 19:24:53 2022 X-Original-To: doc@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4Ly4gp0DGFz4Y2QW for ; Tue, 2 Aug 2022 19:24:54 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4Ly4gn5TpWz4Dhd for ; Tue, 2 Aug 2022 19:24:53 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2610:1c1:1:606c::50:1d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4Ly4gn4X9SzNwy for ; Tue, 2 Aug 2022 19:24:53 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org ([127.0.1.5]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id 272JOr2Z009371 for ; Tue, 2 Aug 2022 19:24:53 GMT (envelope-from bugzilla-noreply@freebsd.org) Received: (from www@localhost) by kenobi.freebsd.org (8.15.2/8.15.2/Submit) id 272JOrVA009370 for doc@FreeBSD.org; Tue, 2 Aug 2022 19:24:53 GMT (envelope-from bugzilla-noreply@freebsd.org) X-Authentication-Warning: kenobi.freebsd.org: www set sender to bugzilla-noreply@freebsd.org using -f From: bugzilla-noreply@freebsd.org To: doc@FreeBSD.org Subject: [Bug 261944] FFS/UFS: explain soft update journaling (SUJ) in documentation and in tunefs(8) Date: Tue, 02 Aug 2022 19:24:53 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Documentation X-Bugzilla-Component: Books & Articles X-Bugzilla-Version: Latest X-Bugzilla-Keywords: X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: mckusick@FreeBSD.org X-Bugzilla-Status: In Progress X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: doc@FreeBSD.org X-Bugzilla-Flags: maintainer-feedback? X-Bugzilla-Changed-Fields: bug_status Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated List-Id: Documentation project List-Archive: https://lists.freebsd.org/archives/freebsd-doc List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-doc@freebsd.org MIME-Version: 1.0 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=freebsd.org; s=dkim; t=1659468293; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3JeT8TLwRxJz7ehoFay4Q1Ddk2buty5arp7x3NCnjUI=; b=g/hORPr976euZO0pP8CQDeyh+vyZHJEwoReMZ8ZzU2ymtHIOgZh5BMSKB+9wIGjTNus8Io Kr/xJTQ2k6fNvGJTU0VwsTJ2sNcQYLs97sjuD064aM2LoSVTRed8tGdqBGVexFmL3D/408 81A3WnySq1Uts7G3Ero84IDM2ZoWNTeU2j0cwiKJq2AcnIlX2vx8lDKFqa5qZxeEnMAcad on/oHmQSce3IuqrTzhfAOpahcYxSAuz/9qXpKJl/9b7scELYhgVSdds01XhNlgMeTK4sQZ t0V7uUtOa3U1HhL48MeXxxCi+RxzNpw/Szqr7rMWXO7baOpUv6fLx7NDcCEo/A== ARC-Seal: i=1; s=dkim; d=freebsd.org; t=1659468293; a=rsa-sha256; cv=none; b=gxcCV+UiOSjbYRitPEfi4LmTMv4pBxC1nY/t2GPzUcPBZuMRzjQ0GhAeJ6g6Ku3RNEMl/p YCRJsKZDuqKUWUAKo8hEDVYeACWhgja9zQA45uuGV0iJx4JTzZ8sWoKLmy9MEiTWZYZoOl oN4T0SwG3/qXj1eiaRAMJcw6T3BKoqq1Dl6tkAJvJsiI2QE2XUKRHv+VF8cFZgMydOa86K EbqSpY40svqsmwKHc03Nx07uEuLoX4UFpk9xfUmvHyx6qElcqZNYwblyOdjAi0NZ+E6iyh Dgz7NqMx3peo6i5Un6mkoxj4ppFEjsaImelkDIFY4rxNOD/FTBGE8oL8rC2k+w== ARC-Authentication-Results: i=1; mx1.freebsd.org; none X-ThisMailContainsUnwantedMimeParts: N https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D261944 Kirk McKusick changed: What |Removed |Added ---------------------------------------------------------------------------- Status|New |In Progress --- Comment #9 from Kirk McKusick --- (In reply to Graham Perrin from comment #8) Here is an expanded explanation of journaled soft updates: I will leave it to you / others to figure out where it should go. My take is that all but the last paragraph should at least be added to tunefs(8). =3D-=3D-=3D Soft updates can add journaling that reduces the time spent by fsck_ffs(8) cleaning up a filesystem after a crash to a few seconds from minutes to hou= rs. It is possible to run fsck_ffs(8) in background on a live filesystem though= the filesystem performance will be about half of normal during the time that the background fsck_ffs(8) is running. Without journaling, the time to recover after a crash is a function of the number of files in the filesystem and the size of the filesystem. With journaling, the time to recover after a crash is a function of the amount of activity in the filesystem in the minute before the crash. Journaled recov= ery time is usually only a few seconds and never exceeds a minute. The drawback to using journaling is that the writes to its log adds an extra write load to the media containing the filesystem. Thus a write-intensive workload will have reduced throughput on a filesystem running with journali= ng. Like all journaling filesystems, the journal recovery will only fix issues known to the journal. Specifically if a media error occurs, the journal will not know about it and hence will not fix it. Thus when using journaling, it= is still necessary to run a full fsck every few months or after a filesystem p= anic to check for and fix any errors brought on by media failure. A full fsck ca= n be done by running a background fsck on a live filesystem or by running with t= he -f flag on an unmounted filesystem. Running a full fsck on a UFS filesystem= is the equivalent of running a scrub on a ZFS filesystem. Presently it is not possible to take a snapshot on a UFS filesystem running with journaled soft updates. Thus it is not possible to reliably dump mount= ed filesystems or to run background fsck on them. The FreeBSD Foundation has sponsored me to make snapshots possible on journaled filesystems. I anticip= ate having that project completed by July 2023. --=20 You are receiving this mail because: You are the assignee for the bug.=