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Robot Dance

Motivation

Tours of high performance computer (HPC) data centers are an increasingly common activity. Most data centers aren't very dynamic: they're rows upon rows of similar racks of computing nodes and disk drawers. The most interesting visual component of these racks are either some blinking lights or large branding/logo skins applied to the outside rack row. Each cluster offers the same viewing experience. Essentially: you've seen one cluster, you've seen 'em all.

Robotic tape libraries can stand out from the crowd in an HPC data center. Unfortunately, well-tuned robotic tape libraries aren't much more active than their compute cluster counterparts. A smoothly running tape library achieves efficiency by moving its robots as little as possible.

So, for tour groups, it's desirable to put the robotic tape libraries into a tour mode. This software package is that tour mode; it makes the robots "dance" and move about. It strives to create visually interesting patterns of movement for the tour groups to observe.

Pre-Reqs

  • Oracle StorageTek SL8500 tape libraries
  • Oracle StorageTek ACSLS library control software
  • Expect

Quick Start

There are three modules that make up this package:

  • trd_dance.bash: The user interface. It's meant to able to run on any node, as long as it shares a filesystem (NFS, etc.) with the ACSLS server.
  • trd_cron.bash: Run this in cron — frequently, say every five minutes — on the ACSLS server as user acsss. This module starts the robot dance, by spawning off individual trd_move.exp instances, and awaits the robot dance termination request. This module requires access to a filesystem (NFS, etc.) shared with the node used to run trd_dance.bash.
  • trd_move.exp: An Expect script that is responsible for moving a pair of cartridges around an SL8500 complex to generate robotic movement. Many of instances of this script are run in parallel by trd_cron.bash to create the overall robot dance. This module needs access to the same filesystem used by the two bash script modules.

To run the robot dance:

% /path/to/trd_dance.bash --start

To stop the robot dance:

% /path/to/trd_dance.bash --stop

Internals

trd_dance.bash will place a sentinel file in the filesystem shared by its host and the ACSLS server. It will log to syslog and HPSS that the robot dance is starting. trd_cron.bash will look for the sentinel file and start up many instances of trd_move.exp. trd_move.exp uses the ACSLS command line processor (cmd_proc) to issue the robotic movement commands. When stopping the robot dance, trd_dance.bash removes the sentinel file and logs to HPSS and syslog that the robot dance is winding down. trd_cron.bash and trd_move.exp exit when the sentinel file disappears from the shared filesystem.

Known Issues & Limitations (a.k.a. opportunities for pull requests and community contributions!)

  • Various external dependencies — command line tools, file system paths, etc. — are hardcoded into this package's various modules
  • This package relies on a non-OSS LLNL software tool named hpsssvc that describes which servers provide which services
  • The tape volumes used by this package are hardcoded into the trd_cron.bash module
  • The number of tape libraries in use is hardcoded into the trd_cron.bash module
  • This package relies on use of genders and a genders schema specific to LLNL
  • In addition to logging to syslog, this package attempts to log to HPSS. Usage of HPSS tools for this logging is hardcoded into trd_dance.bash.