On 31/08/17 03:30 PM, Knurpht - Gertjan Lettink wrote:
That's what I was taught in the late eighties. We backupped ( allow to return to previous day ) and archived ( cumulation for life ).
Indeed. I was taught same in the late 1970s, but that was then, this is now. Back then disk were expensive and easily interchangeable ones more so. We didn't have CDs or DVDs or USB/semiconductor slice removable memory. Heck, the non removable memory for the PDP/11 was expensive enough as it was! We had tape, and the fastest/highest density was 6520bpi and it was SLOW. The 'tower of hanoi' algorithm tried to give a good compromise between backup and archive. The idea was to do incremental backups that became an archive. You tried to deal only with changes over a given period. That way the amount of time you were writing to those slow tape drives was minimised, but you always had enough to make a meaningful recovery to any 'checkpoint'. That was then, this is now. Now I have a, well slow to what I could purchase if I paid more, cable feed that is faster than the PDP/11 tape drives I was using at the beginning for the 1980s. The basic RK05 drive I used on the PDP 11 had a capacity of 2.5 megabytes. My home CPU has a L2 cache of 4096K byes. or is that bits? I also had a RL01 upgraded to RLO2 that could handle 10 megabytes disk packs and had a 1.44Mb/s transfer rate. My home PC has 4 gigabytes of memory. Eventually we upgraded to a RK07 that could handle nearly 30 megabytes. Then there were the RK05 'flying saucer' disk packs :-) Talking about what we considered the norm at the beginning of the 1980s has little relevance now. I can probably back up all of my system, not just my /home, over my network connection to the cloud, faster than I could back up the equivalent on the loadable /usr on the RLO2 to tape in 1982. I have a suspicion that even my SATA DVD reader, should I use it with a ShadowFS, would be faster than the RL02 but I'd have to check the numbers. The PDP-11/45 had a dual bus architecture so autonomous disk transfer could be carried out in parallel with computation and hence appear faster. The recollection are interesting, but the distinctions were forced on us by the limitations of the technology of the time. They no longer apply. -- A: Yes. > Q: Are you sure? >> A: Because it reverses the logical flow of conversation. >>> Q: Why is top posting frowned upon? -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org