LBA Disk Based Recording
The LBA disk based recorders are based on a PCI card built by the Metsähovi Radio Observatory. The system is based on three parts. The VSIC card which converts the S2 data format into VSI format. The data then flows into the VSIB card which slots into a normal PCI slot of a PC and the VLBI data is copied into main memory of the PC. A specially written kernel module (vsib.o) controls the VSIB card and reading of data from the PCI bus. A normal application (vsib_record) then read the data from main memory and writes it to disk. Because the typical data rates are faster than a single disk can sustain, a set of RAID disks are used to get the highest disk I/O. Either hardware RAID, such as the Apple Xserve RAID can be used, or software RAID can be used where normal disks are combined by the Linux operating system to looks like a single large disk. Software RAID has the advantage of being compatible with a large variety of hardware (with hardware RAID you must have exactly the same hardware controller for both recording and playback).
Table of Contents
- Direct disk recording
- Parallel S2 Recording
- Dual DAS Recording
- 64 MHz bandwidth
- Parallel S2 recording
- Scheduled disk based observations
- 64 MHz or Huygens observing
- Narrow bandwidth recording
- vsib_checker
- fauto
- Pre-experiment testing
- Testing during experiment
- Disk based experiments
- Scheduled fringe tests
- Parallel recording for experiment fringe checking