From owner-freebsd-fs@FreeBSD.ORG Wed Nov 14 05:10:40 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 00E639E0 for ; Wed, 14 Nov 2012 05:10:39 +0000 (UTC) (envelope-from chris@behanna.org) Received: from relay01.pair.com (relay01.pair.com [209.68.5.15]) by mx1.freebsd.org (Postfix) with SMTP id A87F78FC08 for ; Wed, 14 Nov 2012 05:10:39 +0000 (UTC) Received: (qmail 83990 invoked by uid 0); 14 Nov 2012 05:03:57 -0000 Received: from 99.120.175.239 (HELO scythe.behanna.org) (99.120.175.239) by relay01.pair.com with SMTP; 14 Nov 2012 05:03:57 -0000 X-pair-Authenticated: 99.120.175.239 Content-Type: text/plain; charset=iso-8859-1 Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Subject: Re: SSD recommendations for ZFS cache/log From: Chris BeHanna In-Reply-To: <50A31D9A.7020200@shatow.net> Date: Tue, 13 Nov 2012 23:03:58 -0600 Content-Transfer-Encoding: quoted-printable Message-Id: References: <57ac1f$gf3rkl@ipmail05.adl6.internode.on.net> <943159E4-8824-4767-96E1-89E8EC69DCDF@behanna.org> <50A31D9A.7020200@shatow.net> To: FreeBSD FS X-Mailer: Apple Mail (2.1499) 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: Wed, 14 Nov 2012 05:10:40 -0000 On Nov 13, 2012, at 22:27 , Bryan Drewery wrote: > On 11/13/2012 10:18 PM, Chris BeHanna wrote: >> On Nov 13, 2012, at 21:51, Stephen McKay = wrote: >>=20 >>> [...lots of good advice about measuring, and lots of good advice = about L2ARC...] >>>=20 >>> I have no way to determine in advance the behaviour of an SSD on >>> power failure so I assume all the ones I can afford have bad >>> behaviour. :-) I know that expensive ones contain capacitors so >>> that power failures do not corrupt their contents. By the nature >>> of advertising (from which we know that any feature not excessively >>> hyped must therefore not be supported), we must conclude that other >>> SSDs by normal operation corrupt blocks on power failure. >>=20 >> If you'll pardon what may be an ignorant question, does this matter = if you have your machine on a UPS, especially if you run upsmon or nut = to do a graceful shutdown when there are n minutes of battery remaining? >=20 > I've had more than 1 UPS battery die on me, resulting in instant = shutoff. Mine always die at 0300 or thereabouts, and none of my UPSen has = an "I know, now STFU" button. I would gather that the extra expense of a capacitor-backed SSD = if you already have a UPS (with relatively new batteries) depends upon = the particular use case. Banking data? Hell yeah. Home office? Meh. = I might lose a few pieces of spam and the last few minutes of work from = my text editor. --=20 Chris BeHanna chris@behanna.org