Mass Storage System

Our mass storage system consists of two components. One is the data transfer system to send the data from the online computer farm to the tape library at the computer center which is located 2 km away from the experimental hall. The other is the high-speed tape drive. The system is shown in Fig. . The data transfer system is based on a set of one-way reflective memory modules connected via optical fibres. The point to point transfer rate is about 8 MB/sec. Data from the six online farm crates are first transferred to three intermediate crates and then sent to the computer center via three optical fibres.

Figure: Data storage system that transfers data from the online computer farm to the tape library system.

The data are received by a SUN workstation using a reflective memory module with the S-Bus interface and then written on a tape. The tape drive, SONY DIR-1000, has a capability to record data at a 15 MB/s rate. Three drives are connected to the SUN workstation via the SCSI interface. One tape can contain 80 MB, which corresponds to a total capacity of 24 TB in the tape library. While one of three tape drives is used for recording, the second one stands by with a loaded tape, and the third one is reserved as a backup drive. By loading tapes on two drives, the tape change procedure completes in a few second although the loading and unloading procedure usually takes 2 minutes.