Fujitsu MHU2100AT 用户手册

 

C141-E202-01EN 6-15 

Methods of using the read segment buffer are explained for following situations. 

In this situations, the top block of read requested data is not stored at all in the 
data buffer.  As a result, all of the read requested data is read from disk media. 

1)  HAP (host address pointer) and DAP (disk address pointer) are defined in the 

head of the segment allocated from Buffer.  (If pre-read is executed, HAP is 
set at the requested data reading position.) 

 

Read segment 

AP (host address pointer) 

 

 

DAP (disk address pointer) 

 

2)  During reading of read requested data, the request data that has already been 

read is sent to the host system. 

 

Read requested data 

Free space 

HAP 

  

    

 

DAP 

Read requested data is 
stored until this point 

 

3)  When reading of read requested data is completed and transfer of the read 

requested data to the host system is completed, reading of the disk continues 
until a certain amount of data is stored.  

 

Read requested data 

Read-ahead data 

 

DAP 

 HAP (stop) 
  

 

 

4)  The following cache valid data is for the read command that is executed next: 

Cache valid data

START LBA

LAST LBA