From owner-freebsd-stable@FreeBSD.ORG Tue Jan 12 00:45:13 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B76201065670 for ; Tue, 12 Jan 2010 00:45:13 +0000 (UTC) (envelope-from fjwcash@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 7CFDE8FC18 for ; Tue, 12 Jan 2010 00:45:13 +0000 (UTC) Received: by pwi15 with SMTP id 15so1929555pwi.3 for ; Mon, 11 Jan 2010 16:45:07 -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:content-type; bh=0s9pbQx5eOQUPvEEITbCaWkzE0BCzqLDksD+Bd4O3iE=; b=vJCgZymiOrRfdgkXArBq0jkmQgDe4xpNg4QNN5aUQcs6dVdScbElwSnxDVePMo43CD PR8h8zjHn3Pd2ul+DbxnpTRmTBTNns8+PfxWJdB07uHCjlftOKMuzLHbhd5oWBEsvcOB fWkJsk1T87I3DbZEWQ1C7lx4vJVoJx3W7PTLE= 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 :content-type; b=szfuqBedGCSQBssdHZXvUX1IHjHW5l6rZj0NpgERQHCYDyeybLGCErNeTbbCmBeYKF kyfdWapC+L0T9EsNusHdP712KvC1aj6fcKPO9+pX2BeNKGNp0OxPkSkN95WFMirpVZvg HwSuWpU0RK1nfArgzWwjJ3MQd6FVdeeq5flmo= MIME-Version: 1.0 Received: by 10.142.67.39 with SMTP id p39mr5346463wfa.204.1263257107155; Mon, 11 Jan 2010 16:45:07 -0800 (PST) In-Reply-To: References: <20100110161206.GA86684@plebeian.afflictions.org> <20100110184612.GC86684@plebeian.afflictions.org> <82c4140e1001111529u7d7ac409h63dda4cc10b76522@mail.gmail.com> Date: Mon, 11 Jan 2010 16:45:07 -0800 Message-ID: From: Freddie Cash To: freebsd-fs@freebsd.org, FreeBSD-STABLE Mailing List Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: Subject: Re: ZFS on top of GELI X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Jan 2010 00:45:13 -0000 On Mon, Jan 11, 2010 at 4:24 PM, Dan Naumov wrote: > On Tue, Jan 12, 2010 at 1:29 AM, K. Macy wrote: > >>> > >>> If performance is an issue, you may want to consider carving off a > partition > >>> on that SSD, geli-fying it, and using it as a ZIL device. You'll > probably > >>> see a marked performance improvement with such a setup. > >> > >> That is true, but using a single device for a dedicated ZIL is a huge > >> no-no, considering it's an intent log, it's used to reconstruct the > >> pool in case of a power failure for example, should such an event > >> occur at the same time as a ZIL provider dies, you lose the entire > >> pool because there is no way to recover it, so if ZIL gets put > >> "elsewhere", that elsewhere really should be a mirror and sadly I > >> don't see myself affording to use 2 SSDs for my setup :) > >> > > > > This is false. The ZIL is used for journalling synchronous writes. If > > your ZIL is lost you will lose the data that was written to the ZIL, > > but not yet written to the file system proper. Barring disk > > corruption, the file system is always consistent. > > > > -Kip > > Ok, lets assume we have a dedicated ZIL on a single non-redundant > disk. This disk dies. How do you remove the dedicated ZIL from the > pool or replace it with a new one? Solaris ZFS documentation indicates > that this is possible for dedicated L2ARC - you can remove a dedicated > l2arc from a pool at any time you wish and should some IO fail on the > l2arc, the system will gracefully continue to run, reverting said IO > to be processed by the actual default built-in ZIL on the disks of the > pool. However the capability to remove dedicated ZIL or gracefully > handle the death of a non-redundant dedicated ZIL vdev does not > currently exist in Solaris/OpenSolaris at all. > > That has been implemented in OpenSolaris, do a search for "slog removal". It's in a much newer zpool version than 13, though. -- Freddie Cash fjwcash@gmail.com