The STAR experiment

Time	Talk	Presenter
14:00	Run VII purchase follow-up and discussion ( 00:10 ) 0 files	Jerome Lauret (BNL)
14:10	tripwire evaluation and configuration ( 00:10 ) 0 files	Mike DePhillips (BNL)
14:20	AOB ( 00:10 ) 0 files	All (All)

2006_mip-.pdf

2006_mip.txt

I plan on "Drupalizing" these pages soon, but for now here are links to Marco's slope calibration and Alex's MIP and Electron calibrations for the 2003 run:

Marco's tower slope calibration

This graph has been extracted for an optimal 30 MB/s capable drive. Both file size and number of files per cartriges have been evaluated.

Introduction

HPSS is software that manages petabytes of data on disk and robotic tape libraries. We will discuss in this section our observations as per the efficiency of accessing files in STAR as per a snapshot of the 2006 situation. It is clear that IO opptimizations has several components amongst which:

• Access pattern optimization (request ordering, ...)
• Optimization based on tape drive and technology capabilities
• Miscellaneous technology considerations
  (cards, interface, firmware and driver, RAID, disks, ...)
  
• HPSS disk cache optimizations
• COS and/or PVR optimization

However, several trend have already been the object of past research and we will point to some of those and compare to our situation rather than debating the obvious. Wewill try to keep a focus on measurements in our environment.

Tape drive and technology capabilities

A starting point would be to discuss the capabilities of the technologies involved and their maximum performance and limitations. In STAR, two technologies remain as per 1006/10:

• the 994B drives
• the LTO-3 drives

Access pattern optimization (request ordering, ...)

A first simple and immediate consideration is to minimize tape mount and dismount operations, causing latencies and therefore performance drops. Since we use the DataCarousel for most restore operations, let's summarize its features.