From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phillip Susi Subject: Re: Does dm handle tape devices? Date: Mon, 05 Nov 2007 17:23:56 -0500 Message-ID: <472F97FC.5000509@cfl.rr.com> References: <20071102195126.GA3712@linux.vnet.ibm.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids lemons_terry@emc.com wrote: > Hi > > Thanks for the reply. I have a customer who runs three tape-aware > applications in one Linux system. Two of those applications use device > files (ex., dev/nst0) to access the tape devices, so the persistent > udev-created symbolic links in /dev/tape/by-id and /dev/generic/by-id > will work fine for those applications. > > A third application, alas, uses SCSI IDs to refer to the tape devices. > I've been instructed to seek a persistent naming solution for this > application, too, one that (hopefully) won't require modification of the > application. I started out looking at the QLogic FC HBA's persistence > capability, and saw that it functions at the target level within a > single HBA. But I found that some vendors don't support this method of > persistence, opting instead to use device mapper. > > Hope this is clear. Device mapper has nothing at all to do with persistent device names. Device mapper is a kernel device driver that creates virtual block devices with interesting mappings to underlying block devices, such as raid. Device naming is handled by udev.