> Old stories, old news. A CD-RW drive looks like any other disk drive, > except much slower. Actually, at 16x write, it's about 2.4MB a minute, which is faster than the 8MM tape drive. And if you compress the data at about 6 to 1 using zip-style compression, you get about 14MB a second, wich is as fast as thefast mag tape drives are going (on actualy throughput). Not to mention that you get about 4 GB of AS/400 data (uncompressed) on a 25 cent CD-R (which is what I would use rather than CD-RW). So for about $1.50 a day, you could have PERMANET backup of your AS/400. Mutiple copies for $3.00 a day. That's very cheap insurance. My compression statistic are based on rather limited data. We saw 3X compression on a 2.74 MB library of RPG and CL source and objects. We say 16X compression (94%) on spool files converted to databases and backed up thru savlib. 6X may be a rather low estimate. I'm trying to be conservative. \ And now 24X drives are out. I bought a 16X SONY CD-R/RW writer and put it in my home PC last week- $99. I wrote a backup copy of my favorite XMAS CD , the Narada Nutcracker in about 3 minutes. 24X drives are now about $150. > > Yes it is cheaper, but how does its reliability & infrastructure compare? > > Your mileage may vary. I guess it depends on whether you consider a CD-RW a > decent backup medium. The fact that CDs cost about a buck and a half apiece > (for 700MB, or about 2 bucks a gig) Again, if you get 6X compressin thats about 30 cents a Gigabyte. On CD-R, it's about 6 cents a gigabyte. Fro most people it will be cheaper, given the reliable re-use lifetimes of magnetic tape, to back up permanently on CD. If you factor in the risk factor of accidental reuse of the tapes, or the tape going bad between backups, CD is hundreds of times cheaper. For example. we develop software on PCs (much of which supports AS/400 functions). Every Friday I get a neww CD-R that has all of our program code, backup copies of our development tools and libraries. I've got 50 of these offsite. Do I feel more secure than if I had a daily magtape backup, reusing tapes in a cylce? You bet your sweet bippy I do. > makes it pretty easy to cost justify > double or triple backups; It's not just the cost, it's the practicality. If you get 6X compression, you can therefore make a copy of 4 GB of AS/400 data in under 3 minutes with a 24X drive. 40 GB in 30 minutes or so (assuming two drives and an attentive operator, or a robot CD writer). > it's a lot harder to do that for tapes (e.g., > QIC-150, $18 for 150MB or around $125 a gig). So, if you like two backups > (one onsite, one offsite), and you want redundancy in both places, then I > think you might want to seriously consider CD-RW. And CD-R/RW drives are now out (I just saw one for $300) . They write slower, but with compression you can get about 25 GB (of AS/400 data) on one CD-R or RW. The media is still expensive, about $7.50. But we know that will change. And the drives will speed up soon, I expect. All of this presumes that you do a two stage backup - SAVLIB to a PC with raided hard drives, then compress and write CD/DVD media while the AS/400 goes on it's merry way. Reading and decompression is much faster, so you can read from the CD, decompress, and drive the tape interface at full speed. Not to mention the nearly zero seeks time of random access CD versus serial access tape. Brad Jensen
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