[Disksim-users] access time estimation

[Anjo Vahldiek]

Hi,

Answering this question is not so simple, since I do not know where you 
would like to use the estimate. (outside or within disksim) I'm asuming 
that you would like to get the estimate within disksim, but outside the 
diskctlr. So that you could e.g. decide which disk or replica of content 
should serve the request, if multiple disks/blocks hold the same content 
(but are in different states/content has different location).

I cannot give you an entire recipe, but I think what you're looking for 
can be found in the disk model interface dm_mech_if in diskmodel/dm.h. 
This interface holds functions to account for entire access time, 
rotational or seek latency, translate between various models of state 
representation... I'm not saying that it is very handy to use, but the 
functionality is there...

Now the question is how do you get the implementation of the interface 
for a specific disk and the current state of the disk. Using the getdisk 
(globally available) fct call... It gives back a structure containing 
current state (which is required for most of the interface functions) as 
well as the implementation of the interface.

getdisk itself needs only an integer to return the disk - and this makes 
it tricky to use. Depending on your implementation it can be difficult 
to know which disk should serve the request. The latest point at which 
one can decide the disk is in the controller (smart, simple or your 
implementation).

Anjo

On 10/23/2012 04:13 AM, Abdul Arfan wrote:
> Dear disksim users,
>
> Is it possible to get an estimation of access time of a request in the disksim?
> I have looked at the code and it says that the acctime estimation is
> not currently supported,
> is there any other alternative to do this? the estimated access time
> does not have to be very
> accurate though.
>
> thank you.
>