[Disksim-users] Serious problems using dixtrac extracted parameters

[Mujtaba Tarihi]

Dear all,

I have been attempting to make use of some parameters extracted via
dixtrac, such as the ones graciously provided by Anjo Vahldiek.
However, I have come across very surprising results, performance-wise.
I generated a random trace of aligned 16KB read requests and a
sequential trace of 16KB back-to-back read requests.
This is how long it took to run each trace (it is in milliseconds)
For the record, are the results obtained with the 2GB HP C2490A which
is supplied along with Disksim:
Random: 2232995.378781
Sequential: 624599.551791

To make the comparison (somewhat) fair, I had to use the same random
trace for the larger drives:

And these are the results obtained with the 300GB Maxtor drive:
Random: 237932.073905
Sequential: 619900.348468

And these are the results obtained with the 146GB Maxtor drive:
Random: 345077.024293
Sequential: 329766.817393

And these results are from the 146GB Seagate drive:
Random: 209403.240946
Sequential: 423689.049873

Basically, with the exception of *slight* difference in case of the
146GB maxtor file, the sequential trace takes longer to run, nearly
2.5x times in the worst case!

I just copied the files in the tar.gz files and used them and
layout.mappings is not necessary.

My guess is that the model generated by the tool has issues with the
modelling firmware behavior, something like the scheduling algorithm,
or maybe it is botching up the mappings?

Any help with be more than welcome :)

Regards,
-Tarihi