On 05/15/2015 08:06 AM, James Knott wrote:
On 05/15/2015 12:42 AM, Anton Aylward wrote:
When I say "or similar' I really do mean that in the loosest of terms.
On that drum, there were a couple of "tracks" at the top of the drum, that consisted of ferrite lines printed directly on the bare drum. One was the clock track and the other, the "sector" track, which was used to indicate where the data started. There was no other formatting done, other than physically moving a head, if there was a bad spot on the drum. I used to gap those heads with a strip of bond paper. I could also use the front panel read & write directly to the drum.
In many ways, "how little has changed". Today's high capacity rotating rust uses the out tracks to store what get called "modules" These can be a variety of things that include some of what you mention, call it data about the disk geometry rather than just "where the data starts", the bad sector tables and the mapping of alternate sectors. There may also be 'executable' modules, microcode patches. Two years ago I had a disk crash and took the disk in for repair; the service manager explained much about how 'modern' disks work, of which the above is a synopsis. The 'linear' model we have of disk storage is the one presented to us by the disk software. There is a CompSci saying that many problems can be solved by a level of indirection. Modern disks are making use of that; what we manipulate with 'fdisk' is just another layer of indirection. (lets not even get started on what it takes to get 'solid state disks' to look like SCSI drives!) So having LVM is another layer and the file system yet another layer. All this to make the abstract model easier to manipulate[1]. I don't think there's anything noble about cutting out a layer of indirection, writing to the raw disk. Its not as if this is a 1960 NASA project where every bit of memory represents a ferrite core and an additional gram of weight which means an additional 100kg of fuel to launch. I did that kind of micro-electronics early in my career and boy was I glad when LSI came out and VLSI and semiconductor memory. War Stories of the distant past are just that. its like Survivalists talking about making their own black powder and doing self-loading in their basement. Great, but that's no way to run a modern army. [1] networking is a case in point. TCP is 'end to end' regardless. The layers of abstraction means that the programme and hence the application programmer can write code that works on a LAN, on a WAN or over Wifi. -- 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