[Disksim-users] Disk Transfer Time questions

[Yipkei Kwok]

Hi,

Question:
1) Transfer time is longer than expected. Why?

Configuration
- I/O driver (FCFS)
- CTLR (FCFS)
- Disk (IBM 18es, prefetching/cache disabled, FCFS)

Read transfer time:
BUS (between CTLR and disk): .0512ms

Bulk sector transfer time:
CTLR: 0.0ms
disk: .101ms

Request size: 4 blocks

With 1 disk, the "Disk Transfer time average" is 25.05ms.

Question 1) Transfer time is longer than expected. Why?
Below is quote from the user manual.
"This specifies the time for the disk to transfer a single 512-byte 
block over the bus. Recall that this value is compared with the 
corresponding bus and controller block transfer values to determine the 
actual transfer time (i.e., the maximum of the three values)."

Disk has the max transfer time (.101ms) per block. but, .101ms * 4 = 
.404 ms << 25.05ms, where 4 is the request size. Does the transfer time 
include any other factor which makes the result that big?

Thank you very much.

Regards,
Yipkei

-- 
********************************************
Yipkei Kwok
Ph.D. Student
Research Assistant
HiPerSys Lab
Department of Computer Science
The University of Texas at El Paso
Phone: 915 747 6433 (O)
E-mail: ykwok2 at miners dot utep dot edu
********************************************