From owner-freebsd-fs@FreeBSD.ORG Fri Feb 15 09:00:30 2013 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id AD1F11D8 for ; Fri, 15 Feb 2013 09:00:30 +0000 (UTC) (envelope-from grarpamp@gmail.com) Received: from mail-oa0-f51.google.com (mail-oa0-f51.google.com [209.85.219.51]) by mx1.freebsd.org (Postfix) with ESMTP id 8021BB0A for ; Fri, 15 Feb 2013 09:00:30 +0000 (UTC) Received: by mail-oa0-f51.google.com with SMTP id h2so3460241oag.24 for ; Fri, 15 Feb 2013 01:00:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:x-received:date:message-id:subject:from:to :content-type; bh=8tqkHSaTydycE50AOzvcBueHh30CqJNZJSRq75RG4Mk=; b=MiSUFVVaEXXKb32SPM8lx7Z4IAeYwWUZYZxzmeKNkrgLZ1OJw+RsgfY40qRCo8uajP OrGyTNUp94sk9wdzfoEZ9hEC3Zkl74WTCR5pGnC+Em1UP7kYk6kdNA6TC1LMsnG5ZGko oTSnrO6FCes43s79lLYCIQq9MhxdCfQohgXte7lMPfnpsByqwnWMqjLPWpHt4VG0O9mt bvocrG3tEh5Oc0y462BsHfcPP6KDm/55l+2GylVZLPV9wjUm6ukAoVvP/icRZxa10CuH kIRqVuGRuXZBf5xWJ04B1n6lhUrqwxroW0242rkc1FtQ2aLq/IUdi45GqfPmF9+oRz1t 9jRA== MIME-Version: 1.0 X-Received: by 10.60.24.135 with SMTP id u7mr1201133oef.90.1360918823663; Fri, 15 Feb 2013 01:00:23 -0800 (PST) Received: by 10.60.146.203 with HTTP; Fri, 15 Feb 2013 01:00:23 -0800 (PST) Date: Fri, 15 Feb 2013 04:00:23 -0500 Message-ID: Subject: Crazy ZFS ZIL options: md(4) umass(4) From: grarpamp To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Feb 2013 09:00:30 -0000 I have thousands of small files being written most under 8KiB, they either end up being removed or combined in various ways to produce a set of data that is stored long term. I also have tens of 10-50MiB files similarly, but rarely. It's not fully clear to me the benefits of a split ZIL. Some say a split ZIL will ward off some fragmentation, which pushing over 80% I'm sure to see otherwise. Plus a speed boost if on faster media. And maybe even no need to commit some ZIL to disk as small files are removed before ZFS decides to aggregate? Anyway, use case aside, I can put 1GiB of ram as ZIL.Same for 32GiB USB. RAM is obviously fast and power fail prone. USB is slow and power safe. Either could be mirrored, 2xRAM, 2xUSB. - If I lose power on RAM, will the disk still be consistent? - What data integrity does ZIL have? None? ZFS dataset's sha256? - Any production experiences with this crazy ideas? Thx.