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270 lines
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<TITLE>Linux - Optical Disk HOWTO : Phase Change Optical Technology </TITLE>
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<LINK HREF="Optical-Disk-HOWTO-8.html" REL=next>
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<LINK HREF="Optical-Disk-HOWTO-6.html" REL=previous>
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<LINK HREF="Optical-Disk-HOWTO.html#toc7" REL=contents>
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<A HREF="Optical-Disk-HOWTO-8.html">Next</A>
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<A HREF="Optical-Disk-HOWTO.html#toc7">Contents</A>
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<HR>
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<H2><A NAME="s7">7. Phase Change Optical Technology </A></H2>
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<P>
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<H2><A NAME="ss7.1">7.1 Introduction</A>
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</H2>
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<P>Optical Phase Change technology is used to create "In Phase" or "Out of
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Phase" bits on a special media for phase change writing. The drive uses a
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LASER of different power levels or LASER intensities to produce this effect.
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One power level allows the media to flow into a crystalline form while the
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other creates an "Out of Phase" condition. The crystallized areas reflect the
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read Lasers beam with a different coefficient of reflectivity than the
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non-crystallized areas. Thus, data can be read from the disk.
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<P>
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<P>What makes the phase change optical disk special is that it the disk is
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formatted with concentric cylinders or tracks with each track being sectored
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much like a magnetic disk or read/write optical disk. The tracks are very close
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so a lot of data can be stored on a disk. This is different from a CD-ROM in
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that it gives your system the look and feel of a magnetic disk. CD-ROMs
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have a spiraling track much like a audio record. Having tracks and sectors
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alone would not make the phase change drive special from optical disk but the
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drive has some very special properties; The phase change drive allows for
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direct overwrite of data which magneto optical can't do inexpensively and the
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media has the very special property of NOT being susceptible to magnetic
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fields or as sensitive to static discharge which gives the media a very long
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shelf life.
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<P>
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<H2><A NAME="ss7.2">7.2 Panasonic LF1000</A>
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</H2>
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<P>
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<H3>POINTS OF INTEREST </H3>
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<P>
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<UL>
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<LI> Read/Write optical disk. </LI>
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<LI> Can read CD-ROMs at 4X speed. </LI>
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<LI> Can read Kodak PhotoCDs. </LI>
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<LI> Media has a 15 Year shelf life. </LI>
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<LI> SCSI-2 Interface. </LI>
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<LI> Track/sector format as opposed to CD-ROMs spiraling record format.</LI>
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<LI> 165ms access time - much better than a tape file restore. </LI>
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<LI> 650Mb data storage per diskette. </LI>
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<LI> Diskettes are about $50 each. </LI>
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</UL>
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<P>
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<H3>THINGS YOU SHOULD KNOW </H3>
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<P>
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<UL>
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<LI>Optical disk format not compatible with any other disk drive. </LI>
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<LI>Vendors don't seem to support UNIX very well - marketing is
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targeted for DOS/Windows and Macintosh. </LI>
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<LI>Do NOT purchase the PD drive which uses the parallel port
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interface - To my knowledge there is no Linux driver for it.</LI>
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</UL>
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<P>
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<H3>Installation</H3>
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<P>The LF1000 is SCSI-2 compatible device. It features a block size of 512 bytes
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and is compatible with the Linux SCSI drivers. This drive was installed on a
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PC compatible AMD 100MHZ 486 with an Adaptec 1542C SCSI bus-master
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controller. To install and mount a disk the following steps were taken;
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<P>
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<H3>Installation steps</H3>
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<P>
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<UL>
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<LI> Install the drive and set the SCSI address to not interfere with other
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SCSI devices. Re-connect all cabling. </LI>
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<LI> Boot the computer. Your SCSI controller should note the new drive. </LI>
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<LI> During the Linux kernel boot, you should see an additional SCSI
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device. In my case, having a magnetic system disk for device /dev/sda
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it shows up as /dev/sdb. </LI>
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<LI> I did NOT partition the device because fdisk issued an overwrite
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warning and I did not want to change anything from a dosemu
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standpoint. </LI>
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<LI> mkfs -t ext2 /dev/sdb </LI>
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<LI> mkdir /pd </LI>
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<LI> mount -t ext2 -o ro,suid,dev,exec,auto,nouser,async /dev/sdb /pd -
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Read only </LI>
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<LI> mount -t ext2 -o defaults /dev/sdb /pd - Mount drive W/R </LI>
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</UL>
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<P><EM>Your ready to "Rock'n'Roll"</EM>
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<P>
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<H3>Usage hints </H3>
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<P>
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<UL>
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<LI>The media which comes with the drive is reported be re-writable about
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500,000 times. This means that it is not advisable to install a live operating
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system such as Linux on the phase change optical drive. These live operating
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systems tend to cache processes to and from disk. Over time this can easily
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approach the phase change media life.
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</LI>
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<LI>Mount drive read only as much as possible.
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</LI>
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<LI>When writing to the drive do so in large chunks. This will help
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reduce any file fragmentation which will require more read seeks.
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</LI>
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<LI>This is however an excellent media for backups, gifs, mpeg or storing
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large programs which you don't use that often. The restore from backup is much
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faster that tape. Backups can be performed using the cp -rp command without
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the need for the ftape driver. This however, will replace symbolic links with
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the actual file. </LI>
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<LI>If while using the PD for writing, You find that the file you just
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wrote to the disk are not there, chances are that the disk write
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protect tab is in write protect mode and you mounted it in read/write mode.</LI>
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</UL>
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<P>
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<H2><A NAME="ss7.3">7.3 Additional Configuration concerns by Jeff Rooze</A>
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</H2>
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<P>Hello,
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<P>I read your article on configuring the Panasonic LF-1000 for
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Linux. I have configured my system so that the optical drive
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has its own device name and the CD-ROM has its own device name.
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This has allowed me to mount either media at any time. I do not
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require any media in the drive when I boot Linux. Also I am using
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the optical drive as an ext2 formatted media.
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<P>I had a couple of minor difficulties in doing so.
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<P>
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First, I had configured my hard drive at SCSI ID 6 and my PD
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at SCSI ID 4. (I wanted to have the hard drive at a higher priority
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that the PD). This caused a problem with the Linux SCSI driver. The
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driver scans the SCSI devices from the Lower SCSI id's to the higher
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(eg: 0 .. 6). Consequently my logical device names were assigned
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differently depending on which type of media was installed in the
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PD drive. This caused a big problem. My Linux partition is on my
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SCSI hard drive and the root device name would change! I corrected
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this problem by modifying the software in the kernel SCSI driver to
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scan the devices in reverse order.
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<P>Second, the distribution Linux kernel does not scan all SCSI LUNS.
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The PD/CD drive has a mode that establishes the CD-ROM at LUN 1 and
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the PD at LUN 0. This mode is selected by the configuration switches
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on the PD/CD drive. Switch #2 should be down (off?). If this switch
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is up (on?), the signature of the device is dependent upon the media
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that is installed and it only reports this device on LUN 0. If no
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media is installed I think it defaults to CD-ROM.
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I am using an Future Domain 16-xx SCSI interface card and the
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software in Linux kernel driver supports an optical device signature
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when scanning the LUNS. I assume that this is standard for most of
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the SCSI drivers. I reconfigured the kernel to enable the "scan all
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LUNS" switch. The kernel then assigns different device names for each
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device. The following is an excerpt from by boot log. You will note a
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series of errors in this log. This is because I did not have the
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optical media installed in the drive and the driver was attempting to
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look at the partition table to determine the block size. Fortunately
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it defaults to 512. I am planning on modifying the Future Domain SCSI
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driver to not do this when it detects the optical device.
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<BLOCKQUOTE><CODE>
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<PRE>
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> scsi0 <fdomain>: BIOS version 3.2 at 0xde000 using scsi id 7
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> scsi0 <fdomain>: TMC-18C50 chip at 0x140 irq 12
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> scsi0 : Future Domain TMC-16x0 SCSI driver, version 5.28
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> scsi : 1 host.
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> Vendor: CONNER Model: CP30545 545MB3.5 Rev: A9AF
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> Type: Direct-Access ANSI SCSI revision: 02
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> Detected scsi disk sda at scsi0, id 6, lun 0
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> Vendor: MATSHITA Model: PD-1 LF-1000 Rev: A109
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> Type: Optical Device ANSI SCSI revision: 02
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> Detected scsi disk sdb at scsi0, id 4, lun 0
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> Vendor: MATSHITA Model: PD-1 LF-1000 Rev: A109
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> Type: CD-ROM ANSI SCSI revision: 02
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> Detected scsi CD-ROM sr0 at scsi0, id 4, lun 1
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> fdomain: Selection failed
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> scsi : detected 1 SCSI cdrom 2 SCSI disks total.
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> SCSI Hardware sector size is 512 bytes on device sda
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> fdomain: REQUEST SENSE Key = 2, Code = 3a, Qualifier = 0
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> last message repeated 3 times
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> sdb : READ CAPACITY failed.
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> sdb : status = 0, message = 00, host = 0, driver = 28
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> sdb : extended sense code = 2
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> sdb : block size assumed to be 512 bytes, disk size 1GB.
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> .
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> .
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> .
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> Partition check:
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> sda: sda1 sda2 sda3
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> scsidisk I/O error: dev 0810, sector 0
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> unable to read partition table of device 0810
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</PRE>
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</CODE></BLOCKQUOTE>
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<P>Third, I modified my file system table (/etc/fstab) to list each
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device but do not attempt to auto mount when booting. I have
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included an excerpt from my fstab. The most important options
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are the noauto, rw(ro), and the checkpass flag.
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<P>To create a ext2 file system on the PD, I used the command
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"mkfs.ext2 -i 2048 /dev/sdb".
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<P>
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<BLOCKQUOTE><CODE>
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<PRE>
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# fstab - List of file systems
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#
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# device mount type options dumpfrequency
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checkpass
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/dev/sdb /optd ext2 rw,user,suid,noauto,sync,exec,dev,umask=0 0 2
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/dev/sr0 /dist iso9660 ro,user,suid,noauto,sync,exec,dev 0 2
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</PRE>
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</CODE></BLOCKQUOTE>
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<P>
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<P>After making these changes, I have had no problems with mounting
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either media. All I need to do is to load the media and type
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"mount /optd" or "mount /dist" and the system does all the rest.
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<P>I hope this information is useful.
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<P>
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<BLOCKQUOTE><CODE>
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<PRE>
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Jeff
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--
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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\ Jeff Rooze -- http://www.treknet.net/~jrooze -- jrooze@treknet.net /
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/ If builders built buildings the way some programmers write \
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\ programs, then the first woodpecker that came along would destroy /
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/ civilization. GERALD WEINBERG \
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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</PRE>
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</CODE></BLOCKQUOTE>
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<P>
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<P>I tried Jeff's suggestion. Here are the steps I performed;
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<UL>
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<LI>Modify my kernel using "make xconfig" in the /usr/src/linux directory
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and installed it. </LI>
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<LI>Change the mode jumper on the PD drive to non-DOS mode. I soldered
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a switch across the mode jumper connections and routed it the the
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back panel. I figured out which switch position was the open position
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and labeled this one for DOS. The other position is of course Linux.
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So before I boot my system I decide which OS I'll be using and set the
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switch accordingly. History shows it staying in the Linux position
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more and more.</LI>
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<LI> Re-boot your system. You should now see multiple LUN show up
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during boot for the PD SCSI device number - It works great!!! If you have
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an older kernel modify the "/usr/src/linux/drivers/scsi/config.in" file.</LI>
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<LI>Update the fstab for both CD and PD drives.</LI>
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<LI>Use appropriate mount command.</LI>
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<LI>"df" to make sure your ready.</LI>
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</UL>
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<P>I did try moving my primary SCSI drive to 6 but experienced some
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difficulties. Can't remember exactly what it was but it may have
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been that my controller "Adaptec 1542" with "Corel SCSI" requires a
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bootable disk and SCSI 0 for the BIOS install to work properly with
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DOS. So I switched it back and enjoyed playing with my properly
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install PD drive! With this configuration "workman" - the audio
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CD player util - works fine.
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<P>
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<P>
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<P>
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<P>
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<HR>
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<A HREF="Optical-Disk-HOWTO-8.html">Next</A>
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<A HREF="Optical-Disk-HOWTO-6.html">Previous</A>
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<A HREF="Optical-Disk-HOWTO.html#toc7">Contents</A>
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