REVIEW: Distributed Schedule Management in the Tiger Video Fieserver

REVIEW: Distributed Schedule Management in the Tiger Video Fieserver

The paper discusses the architecture of Tiger, an on-demand video file
server built on a cluster of relatively inexpensive workstations. The
architecture relies on a single controller machine which acts as the point
of contact for clients and a cluster of workstations or cubs which connect
to the internet using an ATM switched network. Distributing the
organization of the server accross inexpensive machines improves
scalability and fault tolerance although it intoroduces problems in the
administration of the system. Video files are stripped accross hosts in
the system. In order to guarantee quality of service to clients, Tiger
maintains a distributed - although potentially outdated - schedule for all
viewers. Nodes only see part of this schedule, called a collective
hallucination, and at approapriate times they independently send data to
viewers.

By mirroring content accross cubs, Tiger is able to provide fault
tolerance and high availablity, and this is an important factor since
failure of the inexpensive machines employed is inevitable. This is also a
scalable system, although with limitations discussed below. The use of a
global schedule allows Tiger to provide quality of service guarantees to
clients.

Some of the weaknesses of Tiger arise from its need to strip files accross
cubs. Spliting files accross nodes means that for a small enough file,
either small blocks are stored accross all cubs, which is innefficient
because of disk seek time, or files will tend to pile up on lower-numbered
cubs causing an imbalance. Also, changes to the system, such as adding or
removing cubs, are inneficient as it means redoing the layout of disks and
files, although a re-stripe tool is provided.
In addition, the single controller architecture may be an impediment to
scalability and a single point of failure, although Bolosky et al. state
that it is not difficult to distribute its implementation.
Received on Thu Dec 01 2005 - 10:26:50 EST