From owner-freebsd-fs@FreeBSD.ORG Thu Nov 8 21:07:26 2012 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id BCA0D45D for ; Thu, 8 Nov 2012 21:07:26 +0000 (UTC) (envelope-from tevans.uk@googlemail.com) Received: from mail-vb0-f54.google.com (mail-vb0-f54.google.com [209.85.212.54]) by mx1.freebsd.org (Postfix) with ESMTP id 677F28FC0A for ; Thu, 8 Nov 2012 21:07:25 +0000 (UTC) Received: by mail-vb0-f54.google.com with SMTP id l1so4161013vba.13 for ; Thu, 08 Nov 2012 13:07:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=kMheIp0MAIt6u8EsYbp203ums3uwoLEkHzp2UXzZO4U=; b=kO9ik4PCYrkCDF68Bp0WP94rglte/WFB/vfiDN7IoAfdoJklQM8vZDr2orjJzHsS9x rJ1j/KDv5z0P/9pXSPP6xJNICRaC0RP49630jRIKx2N0PQEfQkvHhONaT9Tho0uFcwAB PEOsKx7gjC0mjwcgJvRjWYEgP6czDzTFO/UdZpWrLPXGQUCSo4xQ7/LRrBi+qVpaD2Kh qJyN2GRpG6xOV5oaBvW2Op0Kgi2Qf/haLX8+X3P3qj5h4pe9gCU8tWvLO3wo+JjjC1GV JTKknlhzyu+GtdEAK63zMClOcos2Ag9otOOY6btOJKMF7yFx9xfTbXI99dTgWaTg6WiV YHlg== MIME-Version: 1.0 Received: by 10.52.98.105 with SMTP id eh9mr7433554vdb.11.1352408844775; Thu, 08 Nov 2012 13:07:24 -0800 (PST) Received: by 10.58.233.39 with HTTP; Thu, 8 Nov 2012 13:07:24 -0800 (PST) Date: Thu, 8 Nov 2012 21:07:24 +0000 Message-ID: Subject: SSD recommendations for ZFS cache/log From: Tom Evans To: FreeBSD FS 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: Thu, 08 Nov 2012 21:07:26 -0000 Hi all I'm upgrading my home ZFS setup, and want to speed things up a bit by adding some SSDs for cache/log. I was hoping some more experienced heads could offer some advice on what I've gleaned so far. I've read that the Sandforce based devices get their astonishing write speeds from compressible data, and that on random data, it is significantly worse, so comparing headline write speeds is not that useful. I've also read that MLC flash is significantly slower writing to the 2nd bit, and so the drive firmware will constantly be moving bits in the background from 1st bit to 2nd bit, in order to keep high write speeds, and so the firmware is specially important, which to my mind rules out devices using stock Sandforce firmware (everyone but Intel), and OCZ, who I've read too many horror stories about. This is a home setup, so SLC is out unfortunately. Is it still recommended to have a mirror for log device, now that pools can survive losing a log device unexpectedly? I was planning to get two 128GB drives, and slice them up 4/8/20/96 for UFS root, swap, log, cache respectively, but I could instead get a single larger and faster drive. The drives I am thinking of getting are either Intel 330, Intel 520, Crucial M4 RealSSD or Samsung 830, all in their 120/128GB variants. Any advice gratefully accepted. Cheers Tom