JFFS

jffs - Wikilingue - Encydia

The "System of Files Flash with support to Deals" (or JFFS) is a system of files based on a structure of records NOR uses on memoirs Flash on the part of the company Axis Communication AB. At present, it has been replaced for JFFS2.

Content

1 I design
2 disadvantages
3 see also
4 external linkage

Design

Adding an abstraction level more, JFFS treats to the memoirs flash as a file of circular record. All the changes in files and directories are written in the head of the record in nodes. In every node, a head that contains the metainformation the information themselves is written first and later. The nodes are encandenados for a top displacement in the head. All the nodes begin as valid to turn in obsolete when their new version is created.

Between the head and the tail of the record stays the remaining free space of the system of files, when little of this one stays, a garbage recollector copies the valid nodes of the head to the tail, jumping the obsolete ones, therefore obtaining space.

Disadvantages

In assembly time, the driver must read the whole chain of nodes and keep it in memory, what can make it very slow. The memory consumption is proportional to the number of files in the files system.
The design of circular record means that quite the information of the system of files it is re-written, without importing if it is static or not. Therefore, it generates many unnecessary erasure cycles and reduces the life of the half Flash.