Seagate ST12450W, Руководство по эксплуатации продукта

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ST12450W/WD Product Manual, Rev. A 17
5.6 Caching write data
Write caching is a drive-write operation, which uses a drive’s buffer storage
area where data to be written to the disc is stored while the drive performs
the Write command.
Write caching is enabled along with read caching. Default is cache enabled.
For write caching, the same buffer space and segmentation is used as set
up for read functions. When a write command is issued, the cache is first
checked to see if any logical blocks to be written are already stored in the
cache from a previous read or write command. If there are, the respective
cache segments are cleared. The new data is cached for subsequent read
commands.
If a 10-byte CDB write command (2Ah) is issued with the data page out (DPO)
bit set to 1, no write data is cached, but the cache segments are still checked
and cleared, if needed, for any logical blocks that are being written (see the
SCSI-2 Interface Product Manual).
If the number of write data logical blocks exceeds the size of the segment
being written into when the end of the segment is reached, data is written into
the beginning of the same cache segment, overwriting data that was written
there at the beginning of the operation. However, the drive does not overwrite
data that has not yet been written to the disc.
5.7 Synchronized spindle operation
The synchronized spindle operation allows several drives operating from the
same host to operate their spindles at the same synchronized rotational rate.
Drives operating in a system in synchronized mode increase the system’s
capacity and transfer rate in a cost-effective manner.
The interface consists of a twisted-pair cable, which connects the drives in
the synchronized system in a daisy-chain configuration as shown in
Figure 4.
Figure 4. Synchronized drive interconnect diagram
Master Sync
Source
Host
(or other drive)
Spindle
Control
Drive 1
+5V
RT
J5
11
12
Spindle
Control
Drive 2
+5V
RT
J5
11
12
Spindle
Control
Drive n
+5V
RT
J5
11
12
Sync Interface
System
Interface