From owner-freebsd-fs@freebsd.org Tue Sep 22 22:04:52 2015 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 70A04A076FA for ; Tue, 22 Sep 2015 22:04:52 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from smtp.digiware.nl (unknown [IPv6:2001:4cb8:90:ffff::3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 34D4E1B39; Tue, 22 Sep 2015 22:04:52 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from rack1.digiware.nl (unknown [127.0.0.1]) by smtp.digiware.nl (Postfix) with ESMTP id A8FAB15344D; Wed, 23 Sep 2015 00:04:39 +0200 (CEST) X-Virus-Scanned: amavisd-new at digiware.nl Received: from smtp.digiware.nl ([127.0.0.1]) by rack1.digiware.nl (rack1.digiware.nl [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 9pshHBITbtdI; Wed, 23 Sep 2015 00:04:20 +0200 (CEST) Received: from [IPv6:2001:4cb8:3:1:9d1a:d16e:7a5b:d559] (unknown [IPv6:2001:4cb8:3:1:9d1a:d16e:7a5b:d559]) by smtp.digiware.nl (Postfix) with ESMTPA id D85C9153431; Wed, 23 Sep 2015 00:04:20 +0200 (CEST) Subject: Re: [HAST] ZFS, many disks, write order To: Mark Felder , InterNetX - Juergen Gotteswinter , freebsd-fs@freebsd.org References: <560102BD.6040703@internetx.com> <1442953467.1530841.390840385.067EC1E4@webmail.messagingengine.com> From: Willem Jan Withagen Message-ID: <5601D063.4020104@digiware.nl> Date: Wed, 23 Sep 2015 00:04:19 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <1442953467.1530841.390840385.067EC1E4@webmail.messagingengine.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Sep 2015 22:04:52 -0000 On 22-9-2015 22:24, Mark Felder wrote: > > > On Tue, Sep 22, 2015, at 02:26, InterNetX - Juergen Gotteswinter wrote: >> One of the great Hast Features is that it Hides Disk Failures from ZFS, >> this has been already discussed on this List a few Months ago. >> >> Single ZIL Flash Drive is also not such a great Idea. I whould suggest >> to start from scratch with "ZFS Best Practices". >> > > A single ZIL is not a single point of failure for a few years now. Most > people do not have a ton of data going through the ZIL and if it dies > you only lose those transactions in flight, not your entire pool. Well if you are talking about HA, then it is not quite in order to lose some transactions. Especially if they originate from synchronous writes that are reported committed to the issuer. So why not have 2 in mirror, either both local, or again in local/remote setup. For caches I'd not use this model, since caches are really not critical. If they die, the data is just re-fetched from disk. --WjW