EMC Symmetrix DMX-3, Руководство по эксплуатации продукта

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Elements of a Symmetrix I/O operation 107
Symmetrix DMX-3 Input/Output Operations
If the requested data is not in global memory, the disk director
transfers the data from the disk drive to the global memory, and the
channel director transfers the requested data from the global memory
to the channel.
Figure 23
Symmetrix I/O operations
Channel
director
Channel
Channel
Global
memory
Directory
Channel
director
Global
memory
Directory
Disk
director
Disk
Disk
director
Disk
Read hit
Read miss
Channel Channel
Channel
director
Directory
Global
memory
Channel
director
Directory
Global
memory
Disk
director
Disk
Disk
director
Disk
Fast write Delayed fast write
1 Search-hit global memory directory
2 Transfer to host
3 Update directory
1 Search-miss global memory directory
2 Position R/W head, stage data
3 Transfer to the host
4 Update directory
1 Search-hit global memory directory
2 Transfer to global memory
3 Update directory
4 Destage asynchronously
1 Search global memory directory
(global memory is full)
2 Destage page
3 Update global memory directory
4 Transfer to global memory
5 Update directory
6 Destage asynchronously
5
3
2, 6
4 1
2 1
3
4
2 1
3
3 1
4
2