4.1.2 Disk Scheduling SCAN, C-SCAN and LOOK,C-LOOK in Tamil

[@sathiyavathymurugan7674]

MY UGC NET AND TN SET PREPARATION YOUR VIDEO VERY HELPFUL SIR THANKYOU

[@because2022]

Great to hear that . All the best. Share with your friends too.

[@TSBOFFLINEGAMING]

Sir c-scan and scan la left or right side nu question la kudukalana enna panrathu sir

[@because2022]

Thy wud gve for sure .. sometimes it wl b kind of hint. See examples..

[@letantru5106]

can you guide me to solve this problem, thank you so much: Given a disc with 41 tracks numbered starting at 0 from the outermost track. Each track contains 50 sectors numbered from 0 to 49. Indicate seek time = 10+0.1*T (ms) where T is the number of tracks moving from one request to the next request. The disk rotates once in 50ms. Transmission time for 1 sector is 1ms. Suppose the disk request queue contains the following requests in the form [track:sector]: [10:5], [22:9], [20:21], [21:9], [2:10], [40:45], [6:7], [38:9] The current disk read-write head is located at sector 0 track 20. The disk access time to meet the requirements according to the SCAN algorithms (disc head is aiming at track 40) is ?

[@because2022]

Is it from some competitive exam? Give me some time and send a copy to my mail [e-mail]. I will solve and send to you.

[@SyedRasheed-rc6zp]

7:32 la 199-183 podanuma sir because 199 request nu ques laiye kudukala but namma disk end varaikum poganum la sir ....

[@because2022]

In question they will give total number of cylinders. For this eg its 200. Thats why we take from 0 to 199

[@dhanasekaran.g4032]

Sir diff ezhudanuma 5:55 199-0

[@because2022]

@@dhanasekaran.g4032 Yes

[@KARTHIKRAJS-cy9zh]

i have doubt? 199 is not in the question?btut u marked it as the end? 183 it should be??isnt it? or straightly we go to the end of the disc?exploiting the question end?

[@because2022]

They would have given total cylinders as 200. Thats why 0 to 199

[@Sangamithra_3]

Sir there is 200 so we ended up with 199 that's ok but in which claculation u took 189 inbetween

[@because2022]

@@Sangamithra_3 189 was by mistake. Thats why I have striked it out also.

[@Sangamithra_3]

@@because2022 oh sorry sir...I got it thanks 🙏

[@harithavarshini4690]

236 movements for SCAN

[@because2022]

Correct.

[@Sangamithra_3]

Sir question dha illaye aprom yen 189 and 199 eludhanum... because look and scan ku adhudha difference nu soninga but andha two numbers yen scan la include paninga..plz clarify the doubt sir

[@because2022]

In question they will give total number of cylinders like 200. So we take from 0 to 199.

[@RextonGeorge]

sir what if they haven't mention the direction for SCAN, C-SCAN, LOOK and C-LOOK.

[@because2022]

Then u can take any direction if its not given

[@arunkumarmanokaran7983]

Sir in your ppt for scan the answer is 208 but we simply adding the values i got 236 .which is right can we minuse 2×14 from 236 to get 208.

[@because2022]

Ignore any calculation mistake. Follow the concept clearly.

[@kirann7704]

Nandigal pala ❤🤝

[@because2022]

Most welcome. Keep learning and keep sharing.

[@dropgamingyt5847]

I have a doubt sir. The direction is not given in the book questions sir.

[@because2022]

It will be given in textbook questions and sem also. If not given post the question here.

[@vsvicky5448]

Sir If we start line from 1,the end value will be 200?

[@because2022]

Yes

[@StudyModeON-k6l]

From next time use black background. For more visibility and to reduce eye strain. Please consider this

[@Shinnnnnnes]

Noooo

[@because2022]

Will see

[@prasannaprasanna2423]

Thank you sir .... Great explanation ❤️

[@because2022]

Most welcome

[@shadhujuanshadhu4502]

A disk drive has 300 cylinders numbered 0 to 299. The current head position is at 53. The disk I/O queue contains requests 86, 170, 113, 174,148,150, 102, 75, 215. Starting from the current head position. What is the total distance (in cylinders) that disk arm moves to satisfy all the pending request for a. S-CAN b. C-SCAN my answers, a. scan, 53->0->75->86->102->113->148->150->170->174->215 and cylinder is268 b. 53 -> 75 -> 86 -> 102 -> 113 -> 148 -> 150 -> 170 -> 174 -> 215 -> 299 and cylinder 246 i take left direction for scan, bcus i thought it is the close end to reach and start, but i dont know that was correct or not is this correct mam? they didnt give the direction in this question

[@because2022]

The current head is at 53 and first request is at 86. So you need to move right direction. Plz recalculate once and check. Mam ila sir than,

[@shadhujuanshadhu4502]

@@because2022 ok sir, thank you so much

[@BOT000-r4d]

C scan-386 Look-208 C look-326

[@because2022]

I dont remember exact answer too. If you have followed steps correctly, then its good.

[@info-yv3su]

Suppose that the head of moving head disk with 200 tracks numbered 0 to 199 is currently serving the request at track 143 and has just finished a request at track 125.If the queue request is kept in FIFO order,86, 147, 91, 177, 94, 150, 102, 175, 130. Identify a better disk scheduling algorithm with the minimum seek time can you explain this sir

[@because2022]

For this you just need to try out all algos and find the one with minimum seek time. Head is moving in right side.

[@info-yv3su]

how sir can you explain @@because2022

[@Abirami-ec3zo]

Sir scan la right pogum last 199 reach pannanuma?

[@bangtan_girl6066]

No needed Process complete aana naala 199 end ku poga venam

[@because2022]

I guess its already answerd

[@sukumara6990]

The number of movement in the left direction in c scan is 370..is this correct sir?

[@because2022]

I dont have exact number with me. If calculation is right, the answer will be correct.

[@thamilkumaran282]

386 is correct answer

[@jeyasree605]

Thank you sir for your great explanation 🎉.one doubt sir,in local author book for c-scan they gave one condition (reach one end then reverse without serving the request and reach beginning)and for c-look(reach last request then reverse without serving the request and reach beginning) so reach beginning nu kudutha kandipa right side thana sir move pannanum left side nu question la kuduthalum And Assume the last received was at track 345 and the head is moving towards track 0 nu irrundha left side move pannanuma sir

[@because2022]

Most welcome. No not necessary. We move to any end depending on direction.

[@jeyasree605]

Thankyou sir

[@Hahe2023]

Super teaching sir💯 🎉.I understood clearly. I have a doubt sir ..Will the total disk movement be the same if we move either towards left or right direction in every disk scheduling algorithm. As i tried for c-scan by moving left and i got 386 as the answer 🤔

[@because2022]

Thanks for the feedback. It need not be same alwys. Keep learning and keep sharing with ur frnds and juniors.

[@Hahe2023]

​@@because2022Thanks for the clarification sir ! Sure will share with my friends

[@anbu3349]

Crt dhan 386 dhaan varum

[@gowthamgowtham7523]

Mam Ipo intha sum right direction la potaa right direction fulla poitu nega left varum pothu 0 edukanuma illa venama

[@because2022]

In which algorithm?

[@PRITHIKAM-h3m]

Following are the references attempted to hard disk :67,22,78,34,21,78,99.recommend a suitalbe disk scheduling algorithm and give the reason. sir for this question there are two 78..so we have to solve this differently?and another doubt is here they didnt give the direction..so what i have to do?

[@because2022]

No you can consider the request twice. If no direction given, you can take any direction

[@narmadha7522]

​​@@because2022epdi 2 times edukurathunu sollunga

[@because2022]

@@narmadha7522 Normal way than. After 22 you will process 78 one time... Then again after 21 again you will go to same 78.

[@learnwithrv100]

"Rirection of decreasing track " na left side ahh sir ponum?

[@because2022]

Yes

[@hareshvishal7816]

Sir in local author book excersice they don't mention head direction so can we take in any direction as we want???

[@because2022]

Please refer textbook alwys. In sem direction or some hint wl b given.

[@yashikaramesh18]

Sir no. Of tracks traversed aprm total head movements , aprm total seek distance ellaamey onnu dhana sir?

[@because2022]

Yes

[@Nothing_to_speak]

Sir if they don't give cylinder size ,can I assume some size that is 10 point greater than last disk value

[@because2022]

They will give for sure. If not given you can take just the last disk value also

[@Nothing_to_speak]

@@because2022 ok sir Thank you

[@shadhujuanshadhu4502]

in scan, if we go to the right end first, then final movement is equal to 236? (same as we go for left end first)

[@because2022]

Yes

[@DHIVI-zb2ds]

Sir scan la first end reach panitu return varape service panaumla sir and zero va reach pananuma ( like 99,return 37,14,) after 14 zero 0 reach pananuma sir

[@because2022]

Yes service pannanum but 0 reach aga vendam

[@DHIVI-zb2ds]

@@because2022 tq sir

[@shadhujuanshadhu4502]

c-scan at finish we have to move the to some end, right? like after reaching 37, it has to go to the 199, mam??

[@because2022]

Yes..

[@naveenKumar-jx1uh]

Sir my teacher teach me like in scan both end is reached( so 199 also included). Is that correct sir??

[@because2022]

No. www.geeksforgeeks.org/scan-elevator-disk-scheduling-algorithms/

[@sivakumarsekar1340]

suppose the direction in right in scan , can we include 199 point as end point

[@because2022]

Yes correct

[@alwaysbest5584]

Sir apa namba return vara apo we should not include zero right..e should stop at 14 know sir?

[@because2022]

@@alwaysbest5584 Yes.

[@because2022]

@@alwaysbest5584 Yes

[@dhineshkumarcse5064]

Question la direction kudukala na any direction choose pannalama?

[@because2022]

Yes. Sila time indirect a kuduthirpanga. Like currently head at 53 then it serves 30. It means left movement.

[@rj8110]

Mam suppose if we go to right end.. whether we need to include zero at left end?? In scan

[@because2022]

Not needed.

[@rahulrp3923]

Sir ...ippo scan la right side 199 ponna value change aagum..what to do ????

[@because2022]

Can you ask in detail? Direction wont affect 199.

[@shafacts834]

Sir ethe question tha vantuchu today xam la 🎉

[@because2022]

Great. Keep dng well.

[@PavithraVeeraputhiran]

How to recommend a suitable disk scheduling algorithm sir?

[@because2022]

Which takes shortest number of head movements

[@PavithraVeeraputhiran]

@@because2022 thanks sir

[@yashikaramesh18]

Sir scan la left direction pogum bodhu 0 reach pantu 199 reach panla , ipo right direction ponaa 199 reach pantu 0 va reach panna koodadhaa sir?? Or 199 eh reach pannaama 183 oda vitranumaa? Coz book la 183 oda stop pannirkaanga right direction ku, 0 kum pogala..

[@because2022]

Yes pana kudathu..After 199 you should go to 183 in scan.

[@yashikaramesh18]

@because2022 done sir

[@Kuttipillai]

Sir SCAN la suppose right direction la ponum na till 199 varaikum poganuma??

[@because2022]

Yes

[@Kuttipillai]

@@because2022 ok sir tq✨

[@Issac-qf7fp]

Mam what to do if they gave the starting point and que alone mam?

[@because2022]

You can take any direction. Mam ila sir than

[@Issac-qf7fp]

@@because2022 enaku iniku exam la only starting point and que than sir kuduthanga and end limits kudukala sir ithae sum and so 0 to 183 than sir potu sum eluthiruken

[@Issac-qf7fp]

@@because2022 athu correct or wrong sir and epidi eluthanum

[@because2022]

@@Issac-qf7fp If total number of cylinders not given, then its fine. Its correct only

[@loadedwthpeace6006]

199arm extra add pannuma, questionala 199 kudukalaye..

[@gejendranr2024]

Cylinder value 200.so 0-199

[@because2022]

Yes Cylinder value 200.so 0-199

[@loadedwthpeace6006]

Disk 199 values ah Fcfs and sstf include panni arm varaiyanuma

[@because2022]

@@loadedwthpeace6006 NO

[@PH-cx1vk]

Sir suppose direction right nu kudutha upto 199 varaikum poganuma?

[@because2022]

Yes

[@PH-cx1vk]

@@because2022 Ok Sir. Thank You 🙏🏻

[@DHIVI-zb2ds]

Sir CLook end reach aagama return varapa service pannanuma sir illa venama sir ( return varapa service pananuma venama sir)

[@because2022]

Vendam

[@R.ravikumar5425]

Sir os arrear ku important question sollunga sir

[@because2022]

You can use this kzbin.info/www/bejne/l2q2k2qggNSpr7M

[@divyarosyrcseseca3150]

Sir book la ulla questions la direction kudukkala appo enna sir pannanum

[@because2022]

Please refer textbook only

[@chermarajar3902]

Well explained 😊

[@because2022]

Thank you 🙂

[@RSUGAN-rm7ji]

Sirr direction kudukala na yen pandra ethu sirrrrr?????

[@because2022]

For sure kuduthirpanga. Kudukala na last head and current request no soliirupnaga.

[@anbu3349]

​@@because2022 adha vachu epd sir direction find pananum

[@because2022]

@@anbu3349 Say if last request is 300 and current is greater than 300 , it means it is moving right side or else left.

[@because2022]

@@anbu3349 Say if last request is 300 and current is greater than 300 , it means it is moving right side or else left.

[@rithik243]

Sir question la direction kudukkalanna which side move pannanum

[@because2022]

Definite a kuduthirpanga

[@rithik243]

@@because2022 ok

[@aswinkumar3857]

If the direction is right we will go to the end(199) and return to the remaining work with out (0) Is that correct tell anyone in *SCAN*

[@because2022]

No. I scan we reach one end and reverse direction only but in cscan its different. Refer this www.geeksforgeeks.org/difference-between-scan-and-cscan-disk-scheduling-algorithms/

[@swetham735]

Direction epdi kandu pudikrathu mam

[@because2022]

Will be given in question in two ways. 1. First directly they will specify direction. 2. They will say last request processed was 25 and currently it is at 50. It means we are moving right. If nothing is given you can take any direction.

[@priyadarshini4680]

Sir way particular ah 53

[@because2022]

I am unable to understand your doubt. Please ask in detail

[@ParveenFathimaJ]

Neeha enga work panringa enga clg la vanthu seruga romba la venam oraalvu soli thanga Ena education system uhh chai

[@because2022]

I dont work in any college. I work in I.T. Keep learning.

[@anbu3349]

Thanks a lot sir 😊

[@because2022]

Most welcome

[@rumai3175]

Sir Cscan ku sumission 236 ha??

[@because2022]

Please check again its 382

[@suriyayt3073]

Sir, for C scan it's given as "treats cylinders as a circular list that wraps around from that last cylinder to the first one" If you see then for eg, in right side movement the arm goes from 0 to 199 in order. Ippo circle la 0 to 360 degree poitu odaney aduthathu will be from 0 maari consider panna the seektime from 199 to 0 (199-0) will not be added la sir? appo 382 varrathu la sir? I checked in multiple sites and in an online seektime calculator too. They say 382 dha. But na solradhum crct dhaney?? @because2022

[@suriyayt3073]

@@because2022 One doubt sir... 👆

[@because2022]

@@suriyayt3073 i am nt able to undestand ur point. Plz mail to [e-mail]. i wl gve telegrsm id.

[@anbu3349]

​@@because2022 382 varudhu sir.... Epd 386 varum....

[@R.ravikumar5425]

Arrear exam ku intha question varuma

[@because2022]

It is important question, but sure a sola mudiyathu.

[@R.ravikumar5425]

Sir os arrear ku important sollunga sir

[@subhashenisenthilnathan4629]

Mam 199 other end ah ila question laa vara 183 other end ah mam and 199 ah epdi kothu vathiga mam

[@because2022]

In question they would have specified starting to end.Eg in question you will have "The cylinders are numbered from 0 to 199."

[@peace1536]

Athvum kudukala na ena panrathu sir

[@because2022]

@@peace1536 Kudukala na take nearest round number to maximum request. If max is 185 take 200.

[@vino2741]

If Direction not given for scann

[@because2022]

It will be given for sure. Or it will be given as last request was 40 and currently at 59. That means we should know it was moving right,

[@vino2741]

@@because2022 I will send question can you say me which side it should go

[@vino2741]

Consider a disk queue with requests for I/O to blocks on cylinders. 98 , 183, 37, 122, 14, 124, 65, 67. If the disk head is start at 53, then find out the total head movement with respect to FCFS, SSTF, SCAN, C-SCAN and LOOK scheduling

[@because2022]

@@vino2741 This is very rare. You can use any direction

[@vino2741]

@@because2022 ok sir thank you

[@obulikuppuraj9683]

199 number edhu ku eruku

[@because2022]

Will be given in question about total number of cylinders

[@hemachandran858]

Sir ipo direction ethuvume kudukkala any direction choose pannalam

[@because2022]

Yes if nothing is given.

[@malarkodi720]

Sir exam la total number of cylinders kudukala na enna pandrathu?

[@because2022]

They will give for sure

[@malarkodi720]

Local author book la 3 numericals kudithurukanga sir but adhula direction um kudukala cylinder size um kudukala.. Can you say your mail id sir I'll mail you the problem

[@ssharmi5788]

Thank you so much sir!

[@because2022]

Most welcome!

[@renukasreem1944]

Tq so much sirr

[@because2022]

Most welcome. Keep learning.

[@arulrx45]

Intha question theory a ketta namma la cylinder value eduthukalama

[@because2022]

Yes you can take.

[@divyarosyrcseseca3150]

Sir direction dhan sir kandu pidikka theriyala pls adhu mattum solli thanga sir

[@because2022]

Onume ila. If current head is at 50 and moving towards higher numbers means moving right side. Moving toward lower number means moving left side. Another way: If current head at 40 then next request serviced is 75 means moving right side. Avlo than.

[@divyarosyrcseseca3150]

@@because2022 idhe maari dhan kudupangala sir technical publication book la paththan indha maari kududkkala and oru question paper laum paththan kudukkala sir adhan sum enakku direction mattum therinja fulla pottuduvan sir adhan kekkuran sir

[@divyarosyrcseseca3150]

Starting from the head position appudina namma assending order la write pannitu ahoda starting 0 la irudhu start pannanuma sir

[@divyarosyrcseseca3150]

Moving towards track 0 . direction sollunga sir 😔

[@because2022]

@@divyarosyrcseseca3150 moving towards 0 na left..

[@CSE-MadheshR]

362 for c scan

[@because2022]

Its 382 for C-scan. You can cross verify here also player.uacdn.net/lesson-raw/W541BT2Q0W8YQGXRVMFE/pdf/5376669003.pdf

[@anbu3349]

​@@because2022sir crt dhan... But nega kuduthurka pdf la vera question iruku... Nega vera question example ah eduthurkiga....

[@ShirdiSai4444]

Extraordinary mam🎉🎉🎉🎉

[@because2022]

Thanks a lot.

[@tec_loke]

Sir tecnical publication la seek time oru value la irungu innoru value ku minus pandradhu vera mari iruku na ipo edhu pakanum

[@because2022]

Dnt refer local author..