zillah Posted January 28, 2005 Author Posted January 28, 2005 Thanks agianyes you are rightNow one question left I thing you forgot it, could you please let me know about your idea:Could you please let me know if you agree with this concept or not?:And in the book "Operating System concept" by Silberschatz Fifth Edition page 33:The surface of platter is logically diveded into circular tracks, which are subdivede into secotrs."
jaclaz Posted January 29, 2005 Posted January 29, 2005 The surface of platter is logically diveded into circular tracks, which are subdivede into secotrs.I think it is "almost" right, personally I would have written it as follows:The surface of platter is divided into circular tracks, subdivided into sectors, which represent the minimum (512 byte) addressable unit, logically addressed by the onboard controller.jaclaz
zillah Posted January 29, 2005 Author Posted January 29, 2005 Thanks again, I wish if I can talk to you face to face, this will help me to clarify many things.Now I said in one of my previous response:"In each side(head) of Disk there are numbers of Tracks, within each tarck there is number of sectors (normaly 63 sectors),,,,Am I right?"Could you please let me know how this is difference from the pharagraph that I mentioned it from the book?
jaclaz Posted January 29, 2005 Posted January 29, 2005 Yes, again, in my opinion the sentence:"In each side(head) of Disk there are numbers of Tracks, within each tarck there is number of sectors (normaly 63 sectors)is "almost" right, apart from the (normaly 63 sectors), which is not "normal" , I would have written it as follows:In each platter surface, corresponding to a side or head, of the disk there are a certain number of circular concentric tracks, the length of the track is divided into a number of sectors, each 512 bytes in size; addressing the sectors is made through the onboard controller of the disk. As above, it is practically the same as the (revised) sentence from the book "Operating System concept" by Silberschatz Fifth Edition seen above.What I was trying to explain as an overall concept was the following:1) On the surface(s) of the disk platter(s) there is a total amount of magnetic storage capacity.2) This total amount of capacity is determined by:a) SIZE OF SURFACES (i.e.area of surface(s) by number of platter(s));b) MAGNETIC DENSITY (i.e. how many bytes can be stored per surface unit).3) A part of this capacity is reserved by the manufacturer of the disk and is not accessible by "usual" means.4) Phisically each surface is divided in a number of concentric circular tracks.5) Each track length is sub-divided in minimum addressable units, sized 512 bytes, called sectors.6) Number of sectors in each track is not fixed and is not known, being determined by the manufacturer.7) The onboard controller provides an address translation service to the Operating System, so that each sector in the non-reserved part of the magnetic surface can be uniquely addressed.8) This unique address is a progressive number that identifies a certain sector9) To mantain compatibility with elder Operating System, this addressing system can be "logically" represented as a CHS (Cylinder Head Sector) value;10) This logical representation infers a geometrical model that can be (and normally is) COMPLETELY UNRELATED to the phisycal (real) arrangement of the sectors.11) Addressing sectors by means of this logical representation can simplify calculations in most cases, and allows to mantain the above mentioned compatibility with elder OS's.jaclaz
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