September 21, 2016
Power outage, or no problems? It's been quiet on the 3000-L. "Yeah, too quiet."
In the classic war movies, or a good western with Indian battles, there's the moment when someone notices the silence on the field. "It's quiet out there, Sarge," says the more innocent hero. "Yeah, too quiet," the non-com replies. That kind of quiet might be the sound we're hearing from the 3000-L mailing list today.
It's been five weeks without a new message on the mailing list and newsgroup devoted to MPE and its servers. Advice and solutions has flowed for two decades and more off a mailing list that still has 498 members subscribed. The number of subscribers has remained steady over the last three years. Like the number of migrations in the market, the exit from the list has slowed to a trickle. So has new traffic, of late.
The silence may not be ominous. In 2016 the 3000-L is used almost exclusively to resolve MPE/iX problems. The hardware posts are limited to the rare announcement of used server prices, messages that the members still howl at if they don't include <PLUG> in the subject. The server hasn't been sold by HP in more than a decade, but its owners still don't like to be bugged by sales messages. They solve problems in a grassroots manner. As a notable ballplayer once said, you can look it up. There might be no problems to solve.
However, no messages at all over 35 days sets a new record for the 3000-L quiet. This 3000 resource was much more lively a decade ago. And 20 years back? Well, HP was still selling enough 3000s in the fall of 1996 to be sending its new marketing manager Kathy Fitzgerald to speak at an Indiana RUG meeting about the new servers. There was also advice on storage compression, because compression-enabled DDS drives were becoming more common.
Good advice: If you can find a DDS tape drive from 1996, you should take it out of service. Your MPE server, no. And evergreen advice from the L is still available online. Jeff Kell, the deceased 3000 guru who started the server on a University of Tennessee at Chattanooga server, built it to last.In 1996 people wrote on the L that they understood most drive and backup software vendors recommend against using both hardware and software compression. "You should try each separately and use the technique that achieves the best result consistently," we reported. Mark Klein of ORBiT Software gave an interesting explanation of what was going on and the compression possibilities.
"Actually, there are cases where multiple levels of compression are useful. But first let me describe the various types of compression available.
"Hardware compression is typically LZW or some variant thereof. This type of compression uses a dictionary of repeating strings that can be dynamically determined on the fly and, as such, doesn't require the dictionary to be stored with the data as with other types of compression. There are other types of hardware compression available, but LZW is the most common found on compressing tape drives. LZW can also be done in software.
"Since the compressibility of the data really depends on the data itself, there are instances where negative compression will be achieved as well as instances where very large files can compress down to almost nothing. In fact, I've seen an instance where a large, multi-Gb database that was mostly empty got compressed into less than 32K using LZW.
"LZW is not effective in trying to compress something already compressed with LZW. This can result in negative compression (the resulting data actually gets larger). For that reason, I wouldn't recommend using LZW software compression on top of LZW hardware compression.
"Another type of compression is called run length compression. This is in essence a combination of a length tag and a string. The length indicates how many times to repeat the following string. For example, a line of 80 blanks would be represented by (80," ").
"Now, using a combination of RLC and LZW one can achieve better levels of compression than with one or the other method. So, if you want to use software compression with a hardware compressing tape drive, I would recommend using RLC compression in software."
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Do you still accept questions? We are having issues with our HP3000 and they've been getting progressively worse.
Posted by: Sue Clay | Sep 25, 2016 10:22:06 AM
We're happy to help in whatever way we can.
Posted by: Ron Seybold | Sep 25, 2016 10:45:05 AM
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