From owner-freebsd-questions@FreeBSD.ORG Fri Nov 23 13:45:40 2007 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 78D3216A41A for ; Fri, 23 Nov 2007 13:45:40 +0000 (UTC) (envelope-from cptsalek@gmail.com) Received: from wr-out-0506.google.com (wr-out-0506.google.com [64.233.184.225]) by mx1.freebsd.org (Postfix) with ESMTP id 09B7813C459 for ; Fri, 23 Nov 2007 13:45:39 +0000 (UTC) (envelope-from cptsalek@gmail.com) Received: by wr-out-0506.google.com with SMTP id 68so1593563wra for ; Fri, 23 Nov 2007 05:45:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=lJKSaW6Xtp4tXUMPduW7BI/l9FQB81GVjIbnfGLZFWs=; b=PoEFJRu4Qow7eTVZaP7S57MoLzOKyUiLSRLTOev7H+aZNR9g4E55b9P/h2JWFnjaPQ7JJVTNSAet6KyGRvk8n70YSnSWk2QH3tItt/A4Dsdn1eQL6jQylzRjPQSwM9h6RkGBfD6E0FqOrpPmEOi1Ab+p95Jut1ci6IeqmEZUXDs= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=WUkoMEVC+0nUlS8KrG+3r15n5Di8+JnuAm42rTNatiH8Zz8G3ydaz8YzvZd1Qlf7hXJrMHFaIJ6loY/Ha8YbU1Y1Cy4rcC6G/H6P9AUYjCqQJBWrGjM12auY9csBCZ0JKyr0tJG+MKXkXfD67KPLdzCBuHZNe8V6Cy6kbR+y4VE= Received: by 10.142.237.20 with SMTP id k20mr764606wfh.1195825538024; Fri, 23 Nov 2007 05:45:38 -0800 (PST) Received: by 10.143.45.2 with HTTP; Fri, 23 Nov 2007 05:45:37 -0800 (PST) Message-ID: <14989d6e0711230545k4b32c55bs3564647043f9f4ed@mail.gmail.com> Date: Fri, 23 Nov 2007 14:45:37 +0100 From: "Christian Walther" To: "Jan Catrysse" In-Reply-To: <20071123092146.E0E1B2878E@smtp.proximedia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20071122155640.fa7e0536.wmoran@potentialtech.com> <20071123092146.E0E1B2878E@smtp.proximedia.com> Cc: freebsd-questions@freebsd.org, Bill Moran Subject: Re: RAID1 synchronisation - howto OR not necessary? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 23 Nov 2007 13:45:40 -0000 Hi, On 23/11/2007, Jan Catrysse wrote: > > From: Bill Moran [mailto:wmoran@potentialtech.com] > > Sent: Thursday, November 22, 2007 9:57 PM > > To: Jan Catrysse > > Cc: freebsd-questions@freebsd.org > > Subject: Re: RAID1 synchronisation - howto OR not necessary? > > > > "Jan Catrysse" wrote: > > > [...] > This is what I found in a 3Ware manual: > Verification can provide early warning of a disk drive problem or failure. [...] Yes, it deals with drives failing silently. It's possible that data on a disk can get corrupted. You don't see the error until you read the block the next time. AFAIK the data contained in the bad block is delivered to the CPU/RAM and can cause some damage there. The problem I see with this setup is that you can't know which block is the one that is okay. You need some additional feature like a checksum for each block to check which one is correct. This isn't supported by all file systems, so you can only see that there is a difference between two blocks which sould normally be identical. I doubt that cheep RAID-Controllers have this capability, so you have to stick to some software solution. Does FreeBSD take care about something like this, I mean for software RAIDs? Regards Christian