IEC 62842-2015 pdf free download.Multimedia home server systems – File allocation system with minimized reallocation.
6 Explanation of basic method CoPo2
6.1 Basics
In the history of file allocation, space management was based on the occupation state states of basic allocation unit. Each allocation unit has a one bit state showing occupied or free. In order to allocate a long file, free allocation units are requested of sufficient total size. This bottom up approach is time-consuming and the algorithm itself has the basic problem that it causes fragmentation.
The better way is taking a top-down approach using buddy and improving the buddy to make slack available. Using this, any size expressed by binary notation can be allocated contiguously with concatenation of the divided-partitions each mapped to the binary ones of the binary size.
Based on these considerations, the method is named CoPo2 (concatenation of power-of-2).
6.2 Two choices to apply CoPo2 to an existing partition scheme
6.2.1 General
Unfortunately existing partitions do not use a power-of-two size of basic allocation unit. To apply buddy to such existing partitions, two approaches can be considered. These are applied to existing partitions and to virtual container partitions.
6.2.2 ApplyIng to an existing partition
Buddy could not be applied to size 1011 of basic allocation unit of a partition. If this partition is considered as a concatenation of buddy divided-partitions of sizes 1000(8). 0010(2) and 0001(1) of basic allocation unit, buddy can be applied for each divided-partition as master. Let this method of partitioning be called master partitioning and name the divided-partitions as master divided-partitions. This configuration of partition is defined by a master dividedpartition table and expressed as 1011.
In the following, #1. #8 and #19 are the master divided-partitions and quoted with double parentheses. In this divided-partition numbering, put the most upper level divided-partition as #1 and put continuous numbers to downward and left to right in the same level.IEC 62842 pdf download.