From owner-freebsd-geom@FreeBSD.ORG Tue Oct 4 21:45:53 2011 Return-Path: Delivered-To: freebsd-geom@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2271B106564A; Tue, 4 Oct 2011 21:45:53 +0000 (UTC) (envelope-from mavbsd@gmail.com) Received: from mail-ey0-f182.google.com (mail-ey0-f182.google.com [209.85.215.182]) by mx1.freebsd.org (Postfix) with ESMTP id 4D8428FC0C; Tue, 4 Oct 2011 21:45:51 +0000 (UTC) Received: by eyg7 with SMTP id 7so1355882eyg.13 for ; Tue, 04 Oct 2011 14:45:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; bh=KAIzUQgM7LFsV1guEHuvEFqw7VcrvZRsvK+0l5D5/Kg=; b=t5DhNb29iXxmLczs2ONQUiqsvXaW3+oNOcuTMMZtFfSimWfZCTmA5tMhkPZjQmzDlg ng+rMGaEY+yv/UU1XCxXesEh44grU2mZqsy/VtMYUWTBIxqAsYMlbGdce3oQCeLj1Dgd Wsj0DAz6A8/jqyFaGSzzsREF5j6UeDLhWRLjw= Received: by 10.223.55.146 with SMTP id u18mr2387103fag.108.1317764750972; Tue, 04 Oct 2011 14:45:50 -0700 (PDT) Received: from mavbook2.mavhome.dp.ua (pc.mavhome.dp.ua. [212.86.226.226]) by mx.google.com with ESMTPS id c1sm27027655fab.15.2011.10.04.14.45.49 (version=SSLv3 cipher=OTHER); Tue, 04 Oct 2011 14:45:50 -0700 (PDT) Sender: Alexander Motin Message-ID: <4E8B7E76.5020907@FreeBSD.org> Date: Wed, 05 Oct 2011 00:45:26 +0300 From: Alexander Motin User-Agent: Thunderbird 2.0.0.23 (X11/20091212) MIME-Version: 1.0 To: Miroslav Lachman <000.fbsd@quip.cz> References: <1927112464.20111004220507@serebryakov.spb.ru> <4E8B7A27.5070908@quip.cz> In-Reply-To: <4E8B7A27.5070908@quip.cz> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=windows-1251 Content-Transfer-Encoding: 7bit Cc: lev@FreeBSD.org, current@freebsd.org, freebsd-geom@FreeBSD.org Subject: Re: RFC: Project geom-events X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 04 Oct 2011 21:45:53 -0000 Miroslav Lachman wrote: > Lev Serebryakov wrote: >> One thing is missed from software RAIDs is spare drives and state >> monitoring (yes, I know, that geom_raid supports spare drivers for >> metadata formats which supports them, but it not universal solution). > > I am still missing one thing - dropped provider is not marked as failed > RAID provider and is accessible for anything like normal disk device. So > in some edge cases, the system can boot from failed RAID component > instead of degraded RAID. This can cause data loss or demage. To reliably boot from RAID array, you need help from some RAID BIOS. While booting from correctly working gmirror is possible, it may not be reliable when array is degraded. That is one of the main benefits of the graid, comparing to gmirror -- cooperation with RAID BIOS. Ability to track failed devices also depends on specific metadata format. For example, for Intel RAID BIOS, metadata stored on each disk include information about all other disks used now. As result, if some disk fails and system is unable to update it's metadata any more, that information can still be stored on other devices to prevent disk resurrection in most cases. -- Alexander Motin