Information Technology Reference
In-Depth Information
Transmission
Media Object
Memory
Media Server
Transmission
Media Object
Memory
Media Server
Figure 3.9 A disk array implemented by a disk array controller will be transparent to the media server
application
Transmission
Movie Object
Memory
Media Server
Figure 3.10 The media server implements a striped disk array directly frommultiple independent disks
3.5.3 Multi-Disk Scheduling
Now that data blocks of a media object are spread over multiple disks, we can no longer
schedule each disk independently. We present in this section three multi-disk schedulers and
discuss their strengths and weaknesses.
3.5.3.1 Concurrent Schedule
Figure 3.11 depicts the first multi-disk scheduler - concurrent schedule , for a striped disk array
comprising three disks. Under the concurrent scheduler all disks in the array are synchronized
to retrieve data blocks for the same set of media objects in fixed-duration rounds. For example,
for a d -disk array with retrieval block size of Q bytes, a total of dQ bytes will be retrieved
for each media stream in a service round. Within each service round each disk performs its
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