A Disaster-Tolerant Widely Distributed File System Using Optical Disk Libraries
Masahiro Ueno, Setsuko Murata, Shigetaro Iwatsu, Takaya Tanabe · Japanese Journal of Applied Physics · 1999
We have developed a disaster-tolerant widely distributed data-backup file system that uses optical disk libraries and either simple or advanced small computer system interface (SCSI) extension equipment. The latter includes a redundant arrays of inexpensive disks (RAID) function. To evaluate the basic performance of the developed system, we first used the simple SCSI extension equipment to investigate the effect of the SCSI command-queuing function used in the local SCSI target module and found that it increases the processing speed. We then examined the effect of delay due to the wide distribution and found that read/write throughput was not affected up to distances of 10 km. Next we compared the performance of the backup system using both types of SCSI extension equipment with that without extension equipment. We found that the write speed is about the same for both, but the read speed is slower with the SCSI extension when the data size exceeds 100 kB. Using the advanced equipment to distribute the data to multiple disks solved the problem of non matching read speeds to a certain extent. A backup system using the advanced equipment was applied to a database system by using a database benchmark test program.