From owner-freebsd-fs@FreeBSD.ORG Wed Feb 6 16:42:53 2008 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 6EE4B16A41A for ; Wed, 6 Feb 2008 16:42:53 +0000 (UTC) (envelope-from joe@skyrush.com) Received: from shadow.wildlava.net (shadow.wildlava.net [67.40.138.81]) by mx1.freebsd.org (Postfix) with ESMTP id 2E71013C478 for ; Wed, 6 Feb 2008 16:42:53 +0000 (UTC) (envelope-from joe@skyrush.com) Received: from [67.40.138.82] (crater.wildlava.net [67.40.138.82]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by shadow.wildlava.net (Postfix) with ESMTP id 79A628F394; Wed, 6 Feb 2008 09:42:52 -0700 (MST) Message-ID: <47A9E38B.6040100@skyrush.com> Date: Wed, 06 Feb 2008 09:42:51 -0700 From: Joe Peterson User-Agent: Thunderbird 2.0.0.9 (X11/20071127) MIME-Version: 1.0 To: Bakul Shah References: <20080205190946.3D69C5B59@mail.bitblocks.com> In-Reply-To: <20080205190946.3D69C5B59@mail.bitblocks.com> X-Enigmail-Version: 0.95.5 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: freebsd-fs@freebsd.org Subject: Re: Forcing full file read in ZFS even when checksum error encountered X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Feb 2008 16:42:53 -0000 Bakul Shah wrote: > It could also be a memory error of some sort. Does your > system haev ECC memory? Yes, I always insist on ECC. > Also note that standalone tests do > not seem to catch all sorts of errors that heavy use of Unix > can sometimes trigger on a marginal system. I do plan to do a few more HW checks (cables, etc.), just to make sure. I had been avoiding touching my HW config to preserve the current state of this issue. However, given the coincidental experience Jeremy talked about and the fact that the DMA errors I have seen using ZFS on FreeBSD that I do not see using ZFS-Fuse on the same disk/pool in Linux, I have a gut feeling something funny is going on. > But I agree with you that it would be useful to have a debug > mode where you can get at the data even if it is bad (and a > test mode where you can write bad data on purpose:-). [A > long rant on writing testable code deleted] Yes, the danger of course is if someone forget's that the debug mode is engaged, but I think care could be taken to make sure this cannot easily be done accidentally or massive warnings can be issues to make sure the user knows. > You have access to the zfs sources! At the very least you can > add code to report the bad checksum & offset and see if > matches with checksum of the same block(s) in your known good > copy. Yep, this is my next planned step. Thanks, Joe