Apple Xsan 1.x - Manual (Page 37)

Chapter 3 Deployment Examples 37
The example is based on these assumptions:
 16 editing workstations working with up to 4 streams of DVCPRO 50
 1 editing workstation working with 2 streams of 8-bit 1080i
Deployment Decisions
The following paragraphs answer the planning questions listed in the Xsan
Administrator’s Guide in a way that satisfies the objectives of the video storage
deployment example.
How much storage is needed?
In this example we are dealing with video and want to avoid dropped frames. So,
deciding on the required number of Xserve RAID systems is guided more by the
resulting SAN throughput than by raw storage space. In this example, we need to
support 16 editing stations, each of which might be working with 4 simultaneous
streams of DVCPRO 50 video. As shown in the table on page 19, each stream of
DVCPRO 50 video requires a data rate of 7.7 MB per second.
4 streams x 7.7 MB/s per stream = 31 MB/s per station
16 stations x 31 MB/s per station = 496 MB/s total bandwidth required
A single Xserve RAID system (2 controllers with 7 drives each) can provide
approximately 160 MB/s of throughput in an Xsan volume. Four Xserve RAID systems
can provide 640 MB/s throughput, which should be able to handle the 496 MB/s
requirement with overhead for audio and some additional cushion. So, the DV storage
volume consists of four Xserve RAID systems for data and one half of a system for the
metadata storage pool.
For the high-definition 1080i work, we need to provide one editing station with two
streams:
2 streams x 120 MB/s per stream = 240 MB/s
Two Xserve RAID systems can provide the necessary bandwidth with a cushion.
We’ll incorporate these systems into a second volume for the high-definition work.
Add one Xserve RAID system to support the two metadata storage pools and another
for storing audio files, and a total of eight systems should provide the needed storage
and throughput.