sgs@rand.mel.cocam.oz.au (Stuart Szabo) (06/18/91)
Does anyone know of what advantages 8mm has over DDS tape drives?
Or, are DDS tape drives a better choice?
Which has the better tranfer rates?
Which has better search algorithyms to locate files faster for extraction?
Which one is more of a standard?
Which has lower error rates?
etc, etc, etc, etc.
Thanks,
Stuart Szabo
--
Postal: Co-Cam Computer Services | Stuart Szabo
18-22 Trenerry Cr | sgs@rand.mel.cocam.oz.au
Abbotsford, VIC 3067 | +61 3 412-3411 (voice)
Melbourne, Australia | +61 3 417-7857 (fax) mark@hpcpbla.HP.COM (Mark Simms) (06/20/91)
Firstly, I work for HP on the development of DDS drives. I will try to be unbiased, but take what I say with that in mind. Sometimes we are the victims of our own hype. These are my opinions. They are not those of HP. >> Does anyone know of what advantages 8mm has over DDS tape drives? >> Or, are DDS tape drives a better choice? Which is better depends on many factors. Both technologies have their advantages. >> Which has the better transfer rates? 8mm is noticeably faster. The new 5Gbyte drives can transfer data about 3 times faster than the current generation of DDS drives. This will probably remain the case for the foreseeable future since 8mm has a head start. >> Which has better search algorithyms to locate files faster for extraction? DDS has far better search algorithms, provided your backup application can use them. DDS drives can find a given record or file mark on tape in about 20 seconds on average. The times can be several minutes for a file mark and even longer for a record on 8mm. >> Which one is more of a standard? Depends what you mean by a standard. DDS is an internationally recognized standard accepted by various standards making bodies. 8mm is not. DDS is accepted as an interchange standard by several major computer manufacturers. 8mm is not. DDS is manufactured by several companies. 8mm is manufactured by only one. However, the installed base of 8mm drives is larger than that of DDS drives. DDS is catching up, but what will happen in the long run is anybody's guess. >> Which has lower error rates? I don't know. To be honest, I am not sure if anybody really does. It takes a lot of resources to do error rate testing, so independent testing is very hard. Both are probably "good enough". >> etc, etc, etc, etc. Capacity I am sure you are aware that 8mm wins on capacity or you would have asked the question. However, just for completeness, 8mm drives are now available that will store 5Gbytes on a single tape. DDS drives can store 2Gbytes on a single tape. On drive data compression. DDS drives have been announced that will use hardware data compression to increase capacity and transfer rate. If you have data that is very regular and do not have the processor performance to compress data on the host, then this may be of interest to you. Form factor DDS drives have been announced that are 3.5" form factor. 8mm drives are 5.25" form factor. If you require internal drives in desk top systems then this might be important. Reliability Nobody really knows. Like error rate testing, it takes a lot of resources and there has been little independent testing. In summary, I would say it depends. If transfer rate during backup is the critical issue, then 8mm is the best choice. If host manufacturer support is the issue, then buy whatever the host manufacturer recommends. If rapid restore is critical, then get DDS. If form factor is important then get DDS. For further information try comp.periphs or comp.periphs.scsi. One last comment that I probably shouldn't make, but am going to anyway. If you want responses on notes, then buy DDS. I have never seen any response from Exabyte in notes. Mark Simms ---------------------------------------------------------------------- Opinions expressed are my own and are not intended to be an official statement by Hewlett-Packard Company ---------------------------------------------------------------------- Name: Mark Simms Profession: Software Engineer Occupation: Research and Development Organization: Hewlett-Packard Computer Peripherals Division Unix-mail: mark%hpcpbla@hplb.hpl.hp.com ----------------------------------------------------------------------