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A multiprocessor with eight processors has 20 attached tape drives. there is a large number of jobs submitted to the system, and each requires aMaximum of four tape drives to complete execution. assume that each job starts running with only three tape drives for a long period before requiring theFourth tape drive for a short period toward the end of its operation. also assume an endless supply of such jobs.

a.      Assume the scheduler in the OS will not start a job unless there are four tape drives available. When a job is started, fourdrives are assigned immediately and are not released until the job finishes. What is the maximum number of jobs that can be in progress at once? What is themaximum and minimum number of tape drives that may be left idle as a result of this policy?

If a conservative policy is used, at most 20/4 = 5 processes can be active simultaneously. Because one of the drives allocated toeach process can be idle most of the time, at most 5 drives will be idle at a time. In the best case, none of the drives will be idle.

b.      Suggest an alternative policy to improve tape drive utilization and at the same time avoid system deadlock. What is themaximum number of jobs that can be in progress at once? What are the bounds on the number of idling tape drives?

To improve drive utilization, each process can be initially allocated with three tape drives. The fourth one will be allocated ondemand. In this policy, at most floor(20/3) = 6 processes can be active simultaneously. The minimum number of idle drives is 0 and the maximum number is2.

Consider the following set of processes:

Process Name Arrival Time Processing Time
A 0 3
B 1 5
C 3 2
D 9 5
E 12 5

Perform the same analysis as depicted for this set.

             0         5        10        15        20

             | | | | | | | | | | | | | | | | | | | | |


FCFS     P1 ------

         P2        ----------

         P3                  ----

         P4                      ----------

         P5                                ----------


RR q=1   P1 -- --    --    

         P2    -- --    -- -- --

         P3          --    --

         P4                    -- -- -- -- --

         P5                          -- -- -- ----


RR q=4   P1 ------        

         P2        --------    --  

         P3                ----

         P4                      --------        --

         P5                              -------- --


SPN      P1 ------        

         P2            ----------

         P3        ----

         P4                      ----------

         P5                                ----------


SRT      P1 ------        

         P2            ----------

         P3        ----

         P4                      ----------

         P5                                ----------


HRRN     P1 ------

         P2        ----------

         P3                  ----

         P4                      ----------

         P5                                ----------


FB q=1   P1 -- --      --

         P2    --    --    ---- --

         P3        -- --     

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Operating systems. OpenStax CNX. Aug 13, 2009 Download for free at http://cnx.org/content/col10785/1.2
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