Design a backup strategy for a computer system.One option is to use plug-in exte

Question

Design a backup strategy for a computer system.One option is to use plug-in external disks, which cost $150 for each 500 GB drive. Another option is to buy a tape drive for $2500, and 400 GB tapes for $50 a piece. (These were realistic prices in 2008). A typical backup strategy is to have two sets of backup media onsite, with backups alternatively written on them so incase the system fails while making a backup, the previous version is still intact. There's also a third set kept offsite, with the offsite set periodicallyswapped with an on-site set.

a. Assume you have 1 TB (1000GB) of datato bacp u. How much would a diskl backup system cost?

b. How much would a tape backup system cost for 1TB?

c. How large would each backup have to be in order for a tape strategy to be less expensive?

d. What kind of backup strategy favours tapes?

Explanation / Answer

a) The number of sets=3

A data disk backup cost = (150/500)*1000*3

                                      =0.3*1000*3

                                      =$900

b) Tape backup system cost for 1TB= 2500+(50/400)*1000*3

                                                         =2500+0.125*1000*3

                                                         =2500+375

                                                         =$2875

c) Assume that the required capacity = C GB

            Disk cost =(150/500)*C*3

                            =0.3*C*3 =0.9C

           Tape cost =2500+ (50/400)*C*3

                           = 2500+0.375C

            Tape cost is less than disk cost so that can be shown as

            2500+0.375C< 0.9C

            0.525C>2500

            C>4761.9

d) For large amount data, tapes are favored.      

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