The invention discloses an SCM (storage-class memory) based method for improving the performance of a log 
file system. An SCM serves as a memory device for storing 
metadata and logs of the 
file system, so that the reading and writing of the 
metadata are optimized; coverage writing and additional writing are distinguished, only coverage writing data are written in the logs, additional writing data are directly written in the 
file system, and an update sequence is controlled to ensure the consistency of the file 
system, reduce the log overhead, and improve the performance of the file 
system; and the characteristic of modification by 
byte for the SCM is utilized, and the difference between new and old log blocks is computed, so that the update of log 
byte granularity is realized, and 
log data streams are reduced. The method mainly comprises five operations of storage 
system construction, log writing, 
garbage collection, data back-writing and 
system recovery, can be used for various log file systems, is suitable for constructing high-performance, high-capacity and high-reliability large-sized storage systems, and solves the problems of high extra overhead, high 
metadata back-writing frequency, low 
recovery speed after 
downtime and the like of a log technology in an existing log file system.