From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id l4DGkCvg015036 for ; Sun, 13 May 2007 12:46:12 -0400 Received: from mailmx.futuresource.com (mailmx.futuresource.com [208.10.26.74]) by mx1.redhat.com (8.13.1/8.13.1) with ESMTP id l4DGk9qJ008810 for ; Sun, 13 May 2007 12:46:09 -0400 Received: from ns1.futuresource.com (ns3.futuresource.com [10.207.192.125]) by mailmx.futuresource.com (8.12.11.20060308/8.12.11) with ESMTP id l4DGk84E026317 for ; Sun, 13 May 2007 11:46:08 -0500 Received: from Jill-Mikesells-Computer.local (les2-openvpn.futuresource.com [10.200.1.18]) by ns1.futuresource.com (8.11.6/8.11.6) with ESMTP id l4DGk7h15498 for ; Sun, 13 May 2007 11:46:07 -0500 Message-ID: <464740CD.1080807@gmail.com> Date: Sun, 13 May 2007 11:46:05 -0500 From: Les Mikesell MIME-Version: 1.0 Subject: Re: [linux-lvm] LVM on SATA/PATA disks References: <464672A6.3000408@davidb.org> In-Reply-To: <464672A6.3000408@davidb.org> Content-Transfer-Encoding: 7bit Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development David Brown wrote: > Stuart D. Gathman wrote: > >>> How does SATA fit in with all of this? Is it basically the same >>> limitations on the bus as IDE/PATA, so that you'd really not want to put >>> more than 1 device per bus? >> SATA mandates at most 1 disk per channel, making the issue moot. It is >> still true that there is only one active disk on a bus. But then there >> is only one disk on a bus. > > Newer SATA drives, with proper newer controllers and proper device > driver support will support NCQ (native command queueing), which > allows the drive to re-order requests. It appears that the Linux ACHI > and Nvidia SATA drivers support this capability in recent kernels. > > Of course, any of the re-ordering (SCSI TCQ, or SATA NCQ) requires > filesystem and driver support of write barriers for reliability. > Write barriers are not implement in DM, hence LVM, so there is a > reliability risk in going with this kind of solution. Depending on > the filesystem this can result in power failures resulting in files > having inconsistent data. Are you saying that LVM on SCSI is not safe in this scenario? -- Les Mikesell lesmikesell@gmail.com