Realizing Accelerated Cost-Effective Distributed RAID

The exponential growth in user and application data entails new means for providing fault tolerance and protection against data loss. High Performance Com- puting (HPC) storage systems, which are at the forefront of handling the data del- uge, typically employ hardware RAID at the backend. However, such solutions are costly, do not ensure end-to-end data integrity, and can become a bottleneck during data reconstruction. In this paper, we design an innovative solution to achieve a flex- ible, fault-tolerant, and high-performance RAID-6 solution for a parallel file system (PFS). Our system utilizes low-cost, strategically placed GPUs — both on the client and server sides — to accelerate parity computation. In contrast to hardware-based approaches, we provide full control over the size, length and location of a RAID array on a per file basis, end-to-end data integrity checking, and parallelization of RAID array reconstruction. We have deployed our system in conjunction with the widely-used Lustre PFS, and show that our approach is feasible and imposes ac- ceptable overhead.

The use of Log-file analysis within VMAT audits

OBJECTIVE: This work investigates the delivery accuracy of different Varian linear accelerator models using log-file derived MLC RMS values.

METHODS: Seven centres independently created a plan on the same virtual phantom using their own planning system and the log files were analysed following delivery of the plan in each centre to assess MLC positioning accuracy. A single standard plan was also delivered by seven centres to remove variations in complexity and the log files were analysed for Varian TrueBeams and Clinacs (2300IX or 2100CD models).

RESULTS: Varian TrueBeam accelerators had better MLC positioning accuracy (<1.0mm) than the 2300IX (<2.5mm) following delivery of the plans created by each centre and also the standard plan. In one case log files provided evidence that reduced delivery accuracy was not associated with the linear accelerator model but was due to planning issues.

CONCLUSIONS: Log files are useful in identifying differences between linear accelerator models, and isolate errors during end-to-end testing in VMAT audits. Log file analysis can rapidly eliminate the machine delivery from the process and divert attention with confidence to other aspects. Advances in Knowledge: Log file evaluation was shown to be an effective method to rapidly verify satisfactory treatment delivery when a dosimetric evaluation fails during end-to-end dosimetry audits. MLC RMS values for Varian TrueBeams were shown to be much smaller than Varian Clinacs for VMAT deliveries.