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I bought a Panasonic LF-D201U SCSI internal unit for my testing.
DVD-RAM is optical storage that:
This is a review of an older model. Newer versions are much less expensive (IDE under $150.00 summer 2003) and are multi-purpose, able to write DVD and CD formats. Presently I'm using the Panasonic SW-9571 Combo, which does CD's and DVD's (reads and writes just about anything). It can be bought (bare IDE drive) for under $125.00 (November 2003)
DVD-RAM drives are available in SCSI and IDE models. Pricing at this writing ranges from under $200.00 for the cheapest units to the $700 range for the higher end external units. Media costs about $25 for a single sided 4.7GB disk; double sided and lower capacity disks are also available.
It came with one single sided 4.7GB disk, and I bought two additional double sided disks.
Linux systems see this a a CD-RW, nothing special (other than perhaps setting ide-scsi) is necessary.
On a SCO system, you treat this as a CDROM: mkdev cdrom adds it to your kernel. You can even replace your existing CDROM if you want; the DVD-RAM drive will read (but not write) CDROMS.
There is software for Windows that comes with the unit; it's useless ( and not needed) for Unix or Linux. Modern versions of Linux include drivers that let you create filesystems on DVD-RAM, but for present versions of SCO, you can't do that.
Linux systems can use the IDE versions; the SCO IDE driver doesn't work well enough until 5.0.7; prior to that you must use SCSI. There is a patch for 5.0.6; see http://wdb1.sco.com/kb/showta?taid=125387
However, that does not at all make this useless for a SCO server- in fact, it's the ideal backup method. Realize that you will need special software to use this- you can't "tar cvf /dev/cd0 .", because the CDROM driver (which is what you are using) doesn't even contain a write routine. However, the very latest version of Microlite BackupEDGE SS has the ability to use these drives as a backup device.
Even better, the backup is bootable and includes the recovery programs that let you restore a system. Even when you are just using it to restore a file, the random access capability of a drive allows very quick restores- just seconds to get any file from the media.
With typical compression, you can store over 9 GB on one side of a DVD disk (you flip the cartridge to write the other side of a double-sided disk). Write speed is about 3 GB per hour. The speed and capacity are quite suitable for many typical small business servers.
Although a tremendous amount of data is packed into a small space, you shouldn't experience any problems with scratches and other physical damage. In the first place, the media is packaged in a tough plastic cartridge. The Type 1 media remains in that cartridge forever; the Type 2 can be removed and can be used in some dual purpose CD/DVD drives. But more importantly, the DVD error correction is said to be 10 times better than that used with CDROM's. When used for backup, where there would be no reason to ever remove the media from the cartridge, errors should be effectively non-existent.
Because of the extreme expected life (100,000 writes is 273 years of daily backup!), media cost should be far lower than tape (which typically will survive only a few hundred writes) - in fact, these units could pay for themselves in just a few years in many locations.
Tom Podnar had some important comments in a recent newsgroup post.
Organization: Microlite Corporation From: "D. Thomas Podnar" <[email protected]> X-Mailer: Mozilla 4.76 [en] (Win98; U) X-Accept-Language: en Newsgroups: comp.unix.sco.misc Subject: Re: good tape drive for 5.0.6 References: <[email protected]> <[email protected]> <[email protected]> Date: Wed, 25 Sep 2002 17:56:29 -0400 Bob Meyers wrote: > > "Tony Lawrence" <[email protected]> wrote in message > news:[email protected] > > > > DVDRAM is a far better idea. See /Reviews/dvdram.html > > > > I want to do this DVD-RAM, but I get a lot of negative waves. Some of my > suppliers keep telling me DVD-RAM is on its way to obsolete. I keep waiting > for technology dust to settle - don't want to get caught with a bunch of > obsoletes in addtion to me being obsolete. I wish I had seen this thread a week ago. I'd have commented on it before. I'd been using the mail gateway and not a news reader. Anyway, your suppliers are WRONG. Let me try to set the record straight. It will take a while. For those who don't know, there are FIVE (5) different media formats for DVD. The only thing they have in common is that the media is round, and looks similar. They all have different write methods and capabilities. DVD-RAM DVD-RW DVD-R DVD+RW DVD+R DVD-RAM is designed for data, and happens to work well with video. All the other formats are designed for video and can be used for data. DVD-RAM, DVD-R and DVD-RW come from one camp. DVD-RAM is most often use in a cartridge similar to old CD cartridges, which protects it. It can be written over 100,000 times, and is random access read and write. DVD-RW can be over-written up to 1,000 times. It is a disk-at-once medium, which means you start writing, then write to completion. DVD-R is write once. DVD+RW and DVD+R are from a different camp. DVD+RW can be over-written up to 1,000 times. Technically, and can also be used in a packet writing mode. DVD+R is a write once. All of course have random access once written. What is being "on its way to obsolete" with DVD-RAM devices is their SCSI versions. The original SCSI versions supported DVD-RAM reading and writing, and CD reading. Examples: Panasonic LF-D291U, Hitachi GF-2050. SCSI is the only media that can be easily written on under OpenServer releases trhough 5.0.6. All newer devices have gone to ATAPI only. This is a problem for OpenServer, and I'll explain a bit more later. To POTENTIALLY ease some of the confusion, and to allow you to use the correct media for the job, current generation devices support multiple writing formats. There are CURRENTLY ATAPI devices that support... o DVD-RAM Read/Write o DVD-R Read/Write (Write Once) o CD Read Example. Panasonic LF-D311U, LF-D321U o DVD-RW Read/Write o DVD-R Read/Write (Write Once) o CD-R Read/Write (Write Once) o CD-RW Read/Write Example, Pioneer DVR-A04 o DVD+RW Read/Write o DVD+R Read/Write (Write Once) o CD-R Read/Write (Write Once) o CD-RW Read/Write Example, Hewlett Packard DVD200 As we move along, we'll see even more improvements. The next generation Panasonic, due out next month, supports the following. o DVD-RAM o DVD-RW o DVD-R o CD-R o CD-RW With the right software, you'll simply be able to insert any of those media types and they'll work. Not to be outdone, Sony and NEC have announced products that will bridge the gap between the two camps, by announcing devices that support... o DVD-RW o DVD+RW o DVD-R o DVD+R o CD-RW o CD-R All of the products mentioned are OEMd by many companies, so there may be lots and lots of brand names for the models I've mentioned. Now, on to OpenServer. The device drivers in OpenServer 5.0.6a and earlier do not pass through enough of a command set to support writing to any of the ATAPI devices, or for that matter even a CD writer. So you are limited to SCSI, and that means DVD-RAM only today. Fortunately, under OpenServer 5.0.7, currently in beta, we've worked with the SCO engineering team to ensure that the driver works with all of the current media types. It will be only one of the reasons why 5.0.7 will be a MUST upgrade for many current OpenServer users. Panasonic has a more industrial focus. DVD-RAM is an industrial format. The others, although quite useful for data, are primarily designed to be compatible with your home DVD player, and so are not as good all around as DVD-RAM. This is why, although we currently support all of the media types but DVD-RW, we prefer DVD-RAM for data backups. It isn't going anywhere. Like the other formats, we'll see speed enhancements first, then capacity enhancements moving forward. http://www.maxell-data.com/techinfo/index.shtml This URL has some nice short papers on the various types of DVD media. There is no "driver" support for any of these devices under most operating systems. If you have software that supports them, you write to them directly, then either read from them directly or simply use the CD-ROM driver as necessary. > > I just picked up an IDE HP DVD200i DVD+RW. Microlite says it will work, it > is seen as an IDE CDROM by the OS. Haven't installed it in anything yet. It's not SCSI and it won't work on less than 5.0.7. Our web site is pretty clear on that. Linux or Open UNIX 8 will be fine. -- Best Regards, Tom --- D. Thomas Podnar - President [email protected] Microlite Corporation 724-375-6711 Voice 2315 Mill Street 724-375-6908 Fax Aliquippa PA 15001-2228 888-257-3343 Toll Free Sales +-----------------------------------------------------------+ | Makers of | | BackupEDGE SS - Data Archiving Software For UNIX & Linux | | RecoverEDGE - Network-Enabled Smart Disaster Recovery | | for Linux, Open UNIX 8, UnixWare 7.1, | | and OpenServer 5.0.x. | |http://www.microlite.com ftp://ftp.microlite.com| |Now Supporting: | | Tape, Changer, CD-R/RW, DVD-RAM, DVD-R, DVD+R, and DVD+RW | +-----------------------------------------------------------+
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