Data Transfer Speed; Buffering Operation (Look Ahead/Write Cache); Figure 12. Data Transfer Speed - IBM DTLA-305040 - Deskstar 41.1 GB Hard Drive Specifications

4.4.4 Data transfer speed

Data transfer speed
Disk-Buffer transfer (Zone 0)
Instantaneous - typical
Sustained - typical
Disk-Buffer transfer (Zone 14)
Instantaneous - typical
Sustained - read typical
Sustained - write typical
Buffer-Host (max)

Figure 12. Data transfer speed

Ÿ Instantaneous disk-buffer transfer rate (Mbyte/sec) is derived by the formula
(Number of sectors on a track) * 512 * (revolution/sec)
Note:The number of sectors per track will vary because of the linear density recording.
Ÿ Sustained disk-buffer transfer rate (Mbyte/sec) is defined by considering head/cylinder change time
for read operation. This gives a local average data transfer rate. It is derived by the formula
(Sustained Transfer Rate) = A / (B +C +D ) where
A = (Number of data sectors per cylinder) * 512
B = ((# of Surface per cylinder) - 1) * (Head switch time)
C = (Cylinder change time)
D = (# of Surface) * (One revolution time)
Ÿ Instantaneous buffer-host transfer rate (Mbyte/sec) defines the maximum data transfer rate on the
AT Bus. It also depends on the speed of the host.
The method of measurement is given in 4.4.6, "Throughput" on page 0.

4.4.5 Buffering Operation (Look ahead/Write cache)

To improve the total performance, the drive utilizes a ring buffer for look ahead and write cache. The total
380 KB (DTLA-305XXX) and 1916 KB (DTLA-307XXX) of the buffer is divided into multiple segmented
blocks for write buffer or read buffer use.
Write data will be cached in the buffer for the random block request.
DTLA-305XXX
(Mbyte/sec)
36.5
31.8
17.0
14.8
14.8
100
Deskstar 40GV & 75GXP hard disk drive specifications
DTLA-307XXX
15
(Mbyte/sec)
43.4
37.7
21.7
18.8
18.8
100