From owner-freebsd-geom@FreeBSD.ORG Sat Sep 22 04:20:50 2012 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 285E11065677 for ; Sat, 22 Sep 2012 04:20:50 +0000 (UTC) (envelope-from jacks.1785@gmail.com) Received: from mail-ie0-f182.google.com (mail-ie0-f182.google.com [209.85.223.182]) by mx1.freebsd.org (Postfix) with ESMTP id E95C58FC14 for ; Sat, 22 Sep 2012 04:20:49 +0000 (UTC) Received: by ieak10 with SMTP id k10so5665571iea.13 for ; Fri, 21 Sep 2012 21:20:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=aNNx4qyzpIsKyo+5TyQxIFG9pu1eL5CldVUUDknuy+s=; b=O5sf5A5YAqqen+ggHQ5+8UBUxJ2FrOoYrx+mo1bMGNOuBDG2eeppgd+SEL0tMXOCbp ONzj9BT1ZvYuACj1r4snEq1BECme4HxBnN+Y2RIb2X5sJz+OiMWgcEe8JH7bQxzEiNi0 tvSYIDRI1AvxE2l5+r040wqtQfErNYmHbIyO9+EssOTl1PWtAFeafDe/71gSvWpIIbeS buxoUYSCiIcUjkD6CLp3tum9reEQ6CH+pzqriMNI3G1QKUygghHHoSTNTQzU2x21N9WZ BAcDAQllPun4b8gEIL2YkEcTK7qHViBPwqsGnm1CxFHh2wkCKG+87OB6tsaNWmKU3JRW I/lw== MIME-Version: 1.0 Received: by 10.50.100.166 with SMTP id ez6mr267172igb.55.1348287649141; Fri, 21 Sep 2012 21:20:49 -0700 (PDT) Received: by 10.64.44.105 with HTTP; Fri, 21 Sep 2012 21:20:49 -0700 (PDT) Date: Sat, 22 Sep 2012 09:50:49 +0530 Message-ID: From: Jack To: freebsd-geom@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 Subject: GEOM and CAM pass behaviour 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: Sat, 22 Sep 2012 04:20:50 -0000 Hi all, I would like to know 2 things regarding geom and cam pass driver behaviour. It would be helpful if someone could educate me regarding this. Consider the case where a scsi/ata tape/hard drive is attached to the system after the FreeBSD is booted(from different drive) completely. 1. Is it true that GEOM layer will always taste the (hard drive/tape drive)device whether we access device via cam pass driver or do block access. In other words, say if we never do a block access on the selected device, and we only access this device via cam pass driver, will then Geom will ever have to taste(e.g. for partition table, etc. or for other purposes) this device.? or is it something like, as soon as the device is attached, geom layer will always taste it - it doesn't matter how we access the device. 2. Also, is it possible that while a process is accessing the selected device via cam pass driver, the block access is also possible at that same time, (by same or different process) to that same device. I know that when a process is accessing the device via block access, it is possible for another(or even same) process to access that same device via cam pass driver, but I would like to know whether the other way is true also. Thanks. -- Jack