From owner-freebsd-fs@FreeBSD.ORG Fri Feb 5 10:21:36 2010 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A0BAD106566B for ; Fri, 5 Feb 2010 10:21:36 +0000 (UTC) (envelope-from gary.jennejohn@freenet.de) Received: from mout3.freenet.de (mout3.freenet.de [IPv6:2001:748:100:40::2:5]) by mx1.freebsd.org (Postfix) with ESMTP id 3ACCE8FC13 for ; Fri, 5 Feb 2010 10:21:36 +0000 (UTC) Received: from [195.4.92.24] (helo=14.mx.freenet.de) by mout3.freenet.de with esmtpa (ID gary.jennejohn@freenet.de) (port 25) (Exim 4.70 #1) id 1NdLJf-0002xC-2U; Fri, 05 Feb 2010 11:21:35 +0100 Received: from p57ae1515.dip0.t-ipconnect.de ([87.174.21.21]:31076 helo=ernst.jennejohn.org) by 14.mx.freenet.de with esmtpa (ID gary.jennejohn@freenet.de) (port 25) (Exim 4.72 #1) id 1NdLJe-0006uO-Ep; Fri, 05 Feb 2010 11:21:34 +0100 Date: Fri, 5 Feb 2010 11:21:32 +0100 From: Gary Jennejohn To: freebsd-fs@freebsd.org Message-ID: <20100205112132.184eb12b@ernst.jennejohn.org> In-Reply-To: <20100204210522.GB1733@garage.freebsd.pl> References: <914E8A1F-2FE9-4A7E-9BC7-6174402B57D3@yellowspace.net> <20100128132613.olxiwcq0go0g0w88@www.hmallett.co.uk> <9B1DF836-0CCC-4CB2-B83C-3040428A7344@yellowspace.net> <20100204210522.GB1733@garage.freebsd.pl> X-Mailer: Claws Mail 3.7.4 (GTK+ 2.16.2; amd64-portbld-freebsd9.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Subject: Re: Any news on the HAST Project? X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: gary.jennejohn@freenet.de List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 05 Feb 2010 10:21:36 -0000 On Thu, 4 Feb 2010 22:05:22 +0100 Pawel Jakub Dawidek wrote: > On Wed, Feb 03, 2010 at 03:53:37PM +0100, Lorenzo Perone wrote: > > > > On 28.01.2010, at 14:26, Hywel Mallett wrote: > > > > > About the same time a status update was posted on the FreeBSD Foundation blog at http://freebsdfoundation.blogspot.com/2009/12/update-on-hast-project.html > > > > Thanx, also to pjd's answer. That gives some nice insight already. Great work! HAST could in fact change radically the way of using block devices and distributing mass storage. I look forward to testing it first on a few vboxes and shortly thereafter on real machines. > > > > Really curious on how several things are implemented, e.g. performance / latency / fail / sync issues (what happens for example when a big huge file is written locally on a very fast primary, and there is not enough ram to buffer it before sending it to a secondary.. etc, scenarios like that). > > Every write request is handled synchronously by HAST. It is reported as > completed only when it is stored on local and on remote node. > > > And how well it will do with ZFS too: although ZFS has its 'own' HAST via send/recv (and besides might get its own implementation for some sort of 'streaming' send/recv..) it is also true that it'd allow for some great flexibility in creating primary/secondary volumes (zvols). Just imagining a scenario with sparse zvols and HAST disting them around.. ok ok I stop here :-) > > ZFS send/recv is something else. It can't work synchronously, where HAST > works always that way. This means that when your primary node dies you > won't lose even a single bit of data. > > Although be aware that file systems like UFS can be in inconsistent > state after primary failure, so secondary node after switching to > primary role has to check file system with fsck(8) before mounting it. > This also makes ZFS great choice for running on HAST as 'zpool import' > is very fast as oppose to fsck (at least until Jeff finish his SU+J > project). > I can testify to the benefits of SU+J. I had two crashes on Wednesday and SU+J recovered my file systems in seconds. With fsck it would have taken about 30 minutes. --- Gary Jennejohn