Cloudera Cloudera Certifications CCB-400 Questions & Answers

• Question 11:

  Your data load application is maintaining a custom versioning scheme (not using the timestamp as the version number). You accidentally executed three writes to a given cell all with the same version during which time no flushes have occurred. Which of the three data writes will dBase maintain?

  A. None ofthe writes to cell

  B. The last write to cell

  C. The first write to cell

  D. All ofthe writes to cell

  Correct Answer: C

• Question 12:

  Your client application needs to write a row to a region that has, recently split. Where will the row be written?

  A. One of the daughter regions

  B. The original region

  C. The .META. table

  D. The HMaster

  Correct Answer: A

• Question 13:

  Your client connects to HBase for the first time to road a row user_1234 located in a table Users. What process does your client use to find the correct RegionServer to which it should send the request?

  A. The client looks up the location of ROOT,in which it looks up the location of META, in whichit looks up the location of the correct Users region.

  B. The client looks up the location of the master, in which it looks up the location of META,in which it looks up thelocation of the correct Users region.

  C. The client looks up the location of ROOT in which it looks up the location of the correctUsersregion.

  D. The client queries the master to find the location of the Users table.

  Correct Answer: B

• Question 14:

  You have a table where keys range from "A" to "Z", and you want to scan from "D" to "H." Which of the following is true?

  A. A MultiGet must be issued for rows D, E, F, G, H.

  B. The scan class supports ranges via the stop and start rows.

  C. All scans are full table scans, the client must implement filtering.

  D. In order to range scan, raw scan mode must be enabled.

  Correct Answer: B

• Question 15:

  Your client application connects to HBase for the first time and queries the .META. table. What information does the .META. table provide to your client application?

  A. The location of a Region

  B. The location ofan MMaster

  C. The location of aZooKeeper

  D. The location of a璕OOT璽able

  Correct Answer: A

  Reference:http://hbase.apache.org/book/arch.catalog.html(9.2.2. Meta)

• Question 16:

  You want to do mostly full table scans on your data. In order to improve performance you increase your block size. Why does this improve your scan performance?

  A. It does not. Increasing block size does not improve scan performance.

  B. It does not. Increasing block size means that fewer blocks fit into your block cache. This requires HBase to read each block from disk rather than cache for each scan, thereby decreasing scan performance.

  C. Increasing block size requires HBase to readfrom disk fewer times, thereby increasing scan performance.

  D. Increasing block size means fewer block indexes that need to be read from disk, therebyincreasing scan performance.

  Correct Answer: D

• Question 17:

  From within an HBase application, you would like to create a new table named weblogs. You have started with the following Java code:

  HBaseAdmin admin = new HBaseAdmin (conf);

  HTableDescriptor t = new HTableDescriptor("weblogs");

  Which of the following method(s) would you use next?

  A. admin.createTable(t);admin.enable.Table(t);

  B. admin.createTable(t);

  C. HTable.createTable(t);HTable.enableTable(t);

  D. HTable.createTable(t);

  Correct Answer: D

  Reference:http://linuxjunkies.wordpress.com/2011/12/03/hbase-administration-using-the-java-api- using-code-examples/(creating a table in Hbase, see the code)

• Question 18:

  You have a table with 5 TB of data, 10 RegionServers, and a region size of 256MB. You want to continue with puts to widely disbursed row ids in your table. Which of the following will improve write performance?

  A. Increase your buffer cachein theRegionServers

  B. Increase the number of RegionServers to 15

  C. Decrease your number of RegionServersto 5

  D. Decreaseyour regionsize to 128MB

  Correct Answer: C

• Question 19:

  Given the following HBase dataset, which is labeled with row numbers. . .

  Row # ROW KEY COLUMN+CELL 1 BB002 Column=Comments:C_Author, timestamp=001, value=Diana Mears 2 BB002 Column=Comments:C_Title, timestamp=001, value=Thanks 3 BB001 Column=INFO:Title, timestamp=005, value=HBsase+Hadoop 4 BB001 Column=INFO:Author,timestamp=005,value=Lars George 5 BB002 Column=Comments:C_Text, timestamp=001, value=Any tips on ... 6 BB001 Column=INFO:Text, timestamp=005, value=Some of the ...

  Which of the following lists of row numbers is the correct order that HBase would store this data?

  A. 1, 5, 2, 4, 3, 6

  B. 4, 1, 2, 6, 3, 5

  C. 4, 6, 3, 1, 5, 2

  D. 3, 4, 6, 1, 2, 5

  Correct Answer: C

• Question 20:

  Your client is writing to a region when the RegionServer crashes. At what point in the write is your data secure?

  A. From the moment the RegionServer wrote to the WAL (write-ahead log)

  B. From the moment the RegionServer returned the call

  C. From the moment the RegionServer received the call

  D. From the moment the RegionServer wrote to the MemStore

  Correct Answer: A