Suppose an institution has four caches, referred to as cache-0, cache-1, cache-2 and cache-3. Suppose that the URL hashing scheme operates as follows:
(1) only the host name of the URL is used.
(2) all non-alphabetic characters are ignored.
(3) each alphabetic character is assigned a number corresponding to its position in the alphabet.
(4) these numbers are added modulo 4 to get the hash value of the URL.
(5) if the hash value is 0, the request is directed to cache-0; if 1, the request is directed to cache-1; if 2, the request is directed to cache-2; if 3, the request is directed to cache-3.
For example, the URL http://aaa.bbb.com has hash value 1 + 1 + 1 + 2 + 2 + 2 + 3 +15 + 13(modulo 4) = 0; a request for this URL is sent to cache-0.
[a] Determine to which caches requests for each of the following URLs will be directed:
www.ohecampus.com; www.liv.ac.uk; www.eurecom.uk; www.tiet.ac.in; www.w3c.net; www.embanet.com
[b] Suppose the institutional caches are initially empty. During the first morning of operation, the requests from users at the institution include http://www.ohecampus.com/admissions/index.phtml, http://www.ohecampus.com/programmes/msc.phtml, http://www.ohecampus.com/finance/loanscholarship.phtml, http://www.ohecampus.com/about/brochure.phtml. During the afternoon of the same day, there are seven requests to each of these URLs. Which servers (origin and cache servers) will satisfy these 32 requests?
[c] Suppose now on the second day of operation a fifth cache is added, cache-4 and the algorithm in the browsers is changed to calculate the hash value using modulo 5 rather than modulo 4. Suppose now requests are made for the same six URLs listed in Part a of this problem. What will happen?© BrainMass Inc. brainmass.com October 25, 2018, 1:31 am ad1c9bdddf
[a] Answer to this part is organized in group of three lines (URL, Hash value, Cache used) for each case. "Cache used" is used to mean the same as "Cache to which the request for URL is directed to".
URL = www.ohecampus.com
Hash value = 23+23+23+15+8+5+3+1+13+16+21+19+3+15+13 (modulo 4) = 1
Cache used = cache-1
URL = www.liv.ac.uk
Hash Value = 23+23+23+12+9+22+1+3+21+11 (modulo 4) = 0
Cache used = cache-0
URL = www.eurecom.uk
Hash Value = ...
Solution shows hash value computation for each URL in [a] and [c], in order to determine the cache to which the request for that URL will be directed.
Database Back up
Please discuss what you believe to be a good backup and crisis management strategy considering the following scenario. Provide a detailed explanation of your choices. Be sure to cite your sources.
You work for a small consulting firm with a sterling reputation for high-quality work and outstanding technical aptitude. You've been assigned as the SQL Server 2000 DBA for an e-commerce project based in coastal Florida. Your client is a well-financed, Internet startup firm focusing on creating an online billing system for large hospitals. As a startup firm, they have limited financial resources and must stringently manage their budget.
There are three database environments for your project: development, staging, and production. The development environment is for the web development to create and test their modules and code. The staging environment is where the various components are assembled and tested as a whole. The production environment is the environment that will eventually be your deliverable to the client and will migrate to become the live web presence for the start up.
The client has approached you in the database server room. She's heard there is severe weather coming to the area that may escalate to hurricane status. She would like you to describe in the detail the backup strategies you've developed for each database environment. She'd really like to know how you can save the company money by applying differing backup and crisis management systems to the varying database environments.View Full Posting Details