Question

Please Help with these Operating Systems questions thank you!

1. How is X-RAID or Hybrid RAID different than regular RAID levels?

2.Make a list of six security concerns for a bank’s computer system. Foreach item on your list, state whether this concern relates to physical,human, or operating-system security.

3. How would you protect against a port scan?

4. Calculate the total head movements for the following queues using:

FCFS
SSTF
SCAN
C-SCAN
LOOK
C-LOOK

a. 76, 95, 73, 12, 150, 20, 4, 22, 47, 33, 100 (start = 50, end = 199)

b. 13, 17, 146, 23, 36, 120, 33, 77, 41, 97, 89 (start = 180, end = 199)

5. Compare symmetric and asymmetric encryption schemes, and discuss the circumstances under which you would use each.

6. Describe in your own words the following RAID levels (and state the least number of drives needed to use it):

a. RAID0
b. RAID1
c. RAID5

Answer 1

6)RAID 0:

Here the data is striped into blocks and each is stored in stored in different disk.

Multiple controller must be used to control each and every disk.

RAID 1:

This uses the concept of mirroring in which the data is written twice that is in both data and mirror drive.if the drive fails the controller use either data or mirror drive and continues its work.

RAID 5:

Data blocks are stripped across drives and the parity checksum is stored in adrive .Here least number of drives used is 3 and max number is 16.

5)symmetric cipher is the technique where both the keys used for encryption and decryption are same .

Example:DES and AES.

While in asymmetric cipher there are two keys one is public key and the other is a private key.these two are mathematically related .

Eg:Diffie Hellman ,RSA

1)X RAID simplifies and automate the RAID management process . X RAID has build in management support where the RAID expansion can be done by adding the drives or by replacing the existing drives by larger drive.

3)The portscan can be prevented by using firewall.firewall makes the ports not to respond to the request from port scan.