[AG-TECH] Status of Sessions Captured by Voyager at SCGlobal

Lisa Childers childers at mcs.anl.gov
Wed Nov 21 22:33:11 CST 2001


Dear Folks,

Just wanted to give you an update on the project to archive SCGlobal using
Voyager.

The truck arrived at Argonne from Denver on Tuesday morning (11/20) and 6
icy-cold voyager servers were delivered to our door.  I was advised by folks
here that we should wait until the machines reached room temperature to turn
them on.  By waiting we avoided creating condensation inside the machines
and thus potential electrical mishaps.  At the end-of-day on Tuesday the
boxes were still too cold to power up.

By this morning they had thawed and we began unpacking and bringing up the
servers.  Today we have had a first look at our data.  There is 208G of
SCGlobal content spread across the 6 servers.  Bear in mind that because of
paranoia there is redundancy in some of the sessions.  When possible a
session was recorded simultaneously w/two servers.  I estimate the unique
data size to be roughly 160G.

We have begun the task of reviewing recordings.  Some time today was spent
performing random playbacks in a rough attempt to categorize problems seen
in the recordings.  Current thinking is to code sessions with a grading
system, where sessions are tagged with the following keywords:

SCG5 = problem-free session
SCG4 = problems with the session, but interesting nonetheless
SCG3 = out-of-synch session, potentially interesting
SCG2 = difficult problems with the session resulting in an uninteresting
session
SCG1 = session is unusable

"Problems" so far have included out-of-synch packets, packet loss and
malformed or unknown packetized data.

We have begun moving the data off of the loaner servers.  This is a big
task.  The audio and video data are already heavily compressed, so we can't
make it much smaller than it is in its raw form.  Also it is not as simple
as a straight ftp, because in addition to disk files, native voyager data
include metadata which is stored in a db.  We are currently transferring
data by a custom Voyager session exporter and importer.

One exciting session we ran across today was the presentation from the South
Pole.  17 nodes attended the presentation, contributing 81 video and audio
streams to the session.  There is loss, but it is still way cool.

I'll post an announcement as soon as these data are available on a public
server.

Thanks,
Lisa











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