rampson@uswat.uswest.com (Michael T. Rampson) (07/19/90)
There has been alot of about EXABYTE vs. DAT lately in this news group so I thought I'd throw in my 2 cents. I currently have an HP-DAT which uses a SCSI interface on an HP9000s375. I have 1.8 GB of space on-line but about .9 GB of actual data. Using dump (with parameters of s (size or length of tape) of 17,000 (default bpi) or d (385855 bpi). I originally used 385855 bpi (it comes out to 1.3GB) since this is what HP said it would hold, but they have since come back and said to 17000 (or 1.2 GB). It doesn't matter as long as the overall storage capacity comes out to 1.2 GB. Anyway, I get sustained rates of 10 MB/min and have had peaks of 13.8 MB/min. If anybody has been using HP cartridge tapes, this is a huge improvement for backups of large systems. It takes roughly an hour and 23 minutes (on average) to back my system. I have had no mechanical or other problems (I've only had it for about 3 weeks). The tapes are about $15 bucks (hopefully this price will drop). The seek time on the drive from the begining of the tape to the end seems to be in the neighborhood of 25 secs. Normally this isn't a big deal until you have to restore a file or partition, then this makes a big difference. We also have EXABYTES on our suns. The EXABYTES seem to have a little better throughput (sorry, I don't have numbers forya). Tape initialization, rewind, etc seems to be slower (in the case of initialization it much slower). The tapes are also cheaper ( I think the 8mm are in the neighborhood of $8). We haven't had any problems with the drives themselves, but the SCSI drivers seem to be missing some things or have some proprietary commands (this was a problem, it has been resolved for the most part). We currently have one outstanding problem when trying to use rdump and rrestore (hp -> sun) in that we can't restore since the hp rrestore asks /etc/rmt for a status and our current driver doesn't support it. I've heard rumors that HP is working on an autochanger version (this will allow you to put more than tape in a cage for doing backups > 1.2 GB). I have also heard rumors that someone is looking at doubling the capacity of DAT drives (whether it is a modification of HP/SONY DDS or whatever, I don't know) within the next 2 years. -- These are my own opinions and don't represent anyone else's reality but my own...... rampson@uswat.uswest.com