Hitachi hard disk 0J11285 500 GB 2.5 " 8 MB 0J11285 Guía De Información
Los códigos de productos
0J11285
2
512-byte Read
When the host requests to read a single 512-byte logical block, the hard drive will actually read the entire
4K physical sector containing the requested 4K block containing the 512 bytes. The 512-byte is extracted and
sent to the host. This can be done very quickly.
For example (see Figure 3), a single read of Logical Block #3 will cause Physical Block #1 to be read, and Block #3
is extracted and sent quickly to the host.
4K physical sector containing the requested 4K block containing the 512 bytes. The 512-byte is extracted and
sent to the host. This can be done very quickly.
For example (see Figure 3), a single read of Logical Block #3 will cause Physical Block #1 to be read, and Block #3
is extracted and sent quickly to the host.
512-byte Write (Read-Modify-Write)
When the host attempts to write a single 512-byte logical block, the hard drive will first read the 4K physi-
cal sector containing the 512 bytes that are to be overwritten. Next, it will insert the 512 bytes of new data
and write the entire 4K block of data back to the media. This process is called a “Read-Modify-Write”. The
drive must read the existing data, modify a subset, and then write the data back to the disk. This process can
require additional revolutions of the hard disk.
For example (see Figure 3), a single read of Logical Block #3 will cause Physical Block #1 to be read, and Block #3
is extracted and sent quickly to the host.
cal sector containing the 512 bytes that are to be overwritten. Next, it will insert the 512 bytes of new data
and write the entire 4K block of data back to the media. This process is called a “Read-Modify-Write”. The
drive must read the existing data, modify a subset, and then write the data back to the disk. This process can
require additional revolutions of the hard disk.
For example (see Figure 3), a single read of Logical Block #3 will cause Physical Block #1 to be read, and Block #3
is extracted and sent quickly to the host.
How Does Advanced Format Technology Maintain Performance?
In order to maintain top performance, it is important to ensure that writes to the disk are aligned. Ideally,
writes should be done in 4K blocks, and each block will then be written to a physical 4K sector on the drive.
This can be accomplished by ensuring that the OS and applications write data in 4K blocks, and that the
drive is partitioned correctly.
writes should be done in 4K blocks, and each block will then be written to a physical 4K sector on the drive.
This can be accomplished by ensuring that the OS and applications write data in 4K blocks, and that the
drive is partitioned correctly.
Advanced Format / Technology Brief
Figure 3: 8 x 512-byte Logical Blocks Mapped to 1 x Physical Sector
0
1
2
3
4
5
6
7
Logical Blocks
Host
4K Physical Sector #1
Physical Sectors
0 1 2 3 4 5 6 7
Host
4K Physical Sector #1
Physical Sectors
Host attempts to
write
Logical Block #3. The drive will
read
Physical Sector #1.
0
1
2
3
4
5
6
7
Host
Physical Sectors
3
Drive will
modify
Physical Sector #1 by inserting the Logical Block #3. The drive will
write
Physical Sector #1.
Logical Blocks
Logical Blocks