EMC Symmetrix DMX-3, Руководство по эксплуатации продукта

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108 EMC Symmetrix DMX-3 Product Guide
Symmetrix DMX-3 Input/Output Operations
Read operations There are two types of read operations: read hit and read miss.
Figure 24 on page 108 illustrates the data flow for read operations.
Figure 24
Read operations
Read hit In a read hit operation Figure 24 on page 108 , the requested data
resides in global memory. The channel director transfers the
requested data through the channel interface to the host and updates
the global memory directory. Since the data is in global memory, there
are no mechanical delays due to seek and latency
Figure 25 on
page 108 .
Figure 25 Read hit
Channel
Channel
Channel
director
Channel
director
Global
memory
Global
memory
Read hit
Read miss
Disk
Connect time
Overhead
Total service time