From owner-freebsd-hackers@FreeBSD.ORG Mon Jun 1 08:42:27 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 21BF5106564A for ; Mon, 1 Jun 2009 08:42:27 +0000 (UTC) (envelope-from kraduk@googlemail.com) Received: from mail-ew0-f212.google.com (mail-ew0-f212.google.com [209.85.219.212]) by mx1.freebsd.org (Postfix) with ESMTP id 917BA8FC15 for ; Mon, 1 Jun 2009 08:42:26 +0000 (UTC) (envelope-from kraduk@googlemail.com) Received: by ewy8 with SMTP id 8so4189274ewy.43 for ; Mon, 01 Jun 2009 01:42:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:received:received:from:to:cc:references:subject :date:message-id:mime-version:content-type:content-transfer-encoding :x-mailer:in-reply-to:x-mimeole:thread-index; bh=VEAU/9OgFXNunA2aJEs/Vr36xKZE5N6I7AeXbXUTzuY=; b=Sp8B6heOQQ1IS97Slzn1I9axI+oAt1jDm8h2q7+TtVp5zeJNqtdlxrlb28/D2ZXipS 7JgxCCTkrpuLPYNA8qgmilFrl5YNBux6fbPtnNDJajb2gVhyjb04+BZqnsUCojfsWj0s tSoz7TjDGYl5isQAiMZY3OUeZSG8M4WO9LtfY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=from:to:cc:references:subject:date:message-id:mime-version :content-type:content-transfer-encoding:x-mailer:in-reply-to :x-mimeole:thread-index; b=HaVrx0IFaudeyWzzYInhCE3ftOD2hQtb4AAkiEncKn0tulTrv0AGnT/6K7Bqn4Ws7s p8duT+Kl7wqnh2uBBvloI0lO27gHrGdp3F6XySH8gsp/qROUAav+4Jejfpy5Ut1d4M+y lJVFmhVLPZ+nBuudekIbfC5MgCIQPApma8gE0= Received: by 10.210.105.8 with SMTP id d8mr2870708ebc.77.1243845745273; Mon, 01 Jun 2009 01:42:25 -0700 (PDT) Received: from LTPCSCOTT (e1-1.ns500-1.ts.milt.as9105.net [212.74.112.53]) by mx.google.com with ESMTPS id 4sm6611364ewy.104.2009.06.01.01.42.24 (version=SSLv3 cipher=RC4-MD5); Mon, 01 Jun 2009 01:42:24 -0700 (PDT) From: krad To: "'Wojciech Puchar'" , "'Mike Meyer'" References: <20090530175239.GA25604@logik.internal.network><20090530144354.2255f722@bhuda.mired.org><20090530191840.GA68514@logik.internal.network><20090530162744.5d77e9d1@bhuda.mired.org><20090531201445.GA82420@logik.internal.network><0229B3BF1BE94C82AA11FD06CBE0BDEF@uk.tiscali.intl><20090531235943.GA77374@logik.internal.network><20090531201408.45dd4334@bhuda.mired.org> Date: Mon, 1 Jun 2009 09:42:24 +0100 Message-ID: <442651299CA2445991E65F64AF9E65D7@uk.tiscali.intl> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook 11 In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Thread-Index: AcniT6s9VrLTtiuvSbuSBty7iKcBIQARF3Cg X-Mailman-Approved-At: Mon, 01 Jun 2009 11:24:46 +0000 Cc: freebsd-hackers@freebsd.org, xorquewasp@googlemail.com Subject: RE: Request for opinions - gvinum or ccd? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 01 Jun 2009 08:42:27 -0000 You shouldn't need to alter the copies attribute to recover from disk failures as the normal raid should take care of that. What the copies is useful for is when you get undetected write errors on the drive due to crc collisions or the drive simply being rubbish Zfs will intelligently assign the copies across multiple drives if possible, so if you had 3 vdevs and copies set to three, One copy should end up on each vdev. Note this isn't the same as mirroring, as each vdev could be a raidz2 group. With copies=1 you would get a 3rd of the file on each. With copies 3 you would get a full version of each. This is obviously very costly on drive space though. It is tunable per file system though so you don't have to enable it for the whole pool just the bits you want. -----Original Message----- From: owner-freebsd-hackers@freebsd.org [mailto:owner-freebsd-hackers@freebsd.org] On Behalf Of Wojciech Puchar Sent: 01 June 2009 01:26 To: Mike Meyer Cc: freebsd-hackers@freebsd.org; xorquewasp@googlemail.com Subject: Re: Request for opinions - gvinum or ccd? > Disks, unlike software, sometimes fail. Using redundancy can help modern SATA drives fail VERY often. about 30% of drives i bought recently failed in less than a year. > both checksum on and copies > 1 on, and the latter isn't the > default. It's probably better to let zpool provide the redundancy via > a mirror or raid configuration than to let zfs do it anyway. ZFS copies are far from what i consider useful. for example you set copies=2. You write a file, and get 2 copies. Then one disk with one copy fails, then you put another, do resilver but ZFS DOES NOT rebuild second copy. You need to write a program that will just rewrite all files to make this. _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"