This set of Hadoop Multiple Choice Questions & Answers (MCQs) focuses on “MapReduce Job – 1”.
1. __________ storage is a solution to decouple growing storage capacity from compute capacity.
a) DataNode
b) Archival
c) Policy
d) None of the mentioned
View Answer
Explanation: Nodes with higher density and less expensive storage with low compute power are becoming available.
2. Point out the correct statement.
a) When there is enough space, block replicas are stored according to the storage type list
b) One_SSD is used for storing all replicas in SSD
c) Hot policy is useful only for single replica blocks
d) All of the mentioned
View Answer
Explanation: The first phase of Heterogeneous Storage changed datanode storage model from a single storage.
3. ___________ is added for supporting writing single replica files in memory.
a) ROM_DISK
b) ARCHIVE
c) RAM_DISK
d) All of the mentioned
View Answer
Explanation: DISK is the default storage type.
4. Which of the following has high storage density?
a) ROM_DISK
b) ARCHIVE
c) RAM_DISK
d) All of the mentioned
View Answer
Explanation: Little compute power is added for supporting archival storage.
5. Point out the wrong statement.
a) A Storage policy consists of the Policy ID
b) The storage policy can be specified using the “dfsadmin -setStoragePolicy” command
c) dfs.storage.policy.enabled is used for enabling/disabling the storage policy feature
d) None of the mentioned
View Answer
Explanation: The effective storage policy can be retrieved by the “dfsadmin -getStoragePolicy” command.
6. Which of the following storage policy is used for both storage and compute?
a) Hot
b) Cold
c) Warm
d) All_SSD
View Answer
Explanation: When a block is hot, all replicas are stored in DISK.
7. Which of the following is only for storage with limited compute?
a) Hot
b) Cold
c) Warm
d) All_SSD
View Answer
Explanation: When a block is cold, all replicas are stored in the ARCHIVE.
8. When a block is warm, some of its replicas are stored in DISK and the remaining replicas are stored in _________
a) ROM_DISK
b) ARCHIVE
c) RAM_DISK
d) All of the mentioned
View Answer
Explanation: Warm storage policy is partially hot and partially cold.
9. ____________ is used for storing one of the replicas in SSD.
a) Hot
b) Lazy_Persist
c) One_SSD
d) All_SSD
View Answer
Explanation: The remaining replicas are stored in DISK.
10. ___________ is used for writing blocks with single replica in memory.
a) Hot
b) Lazy_Persist
c) One_SSD
d) All_SSD
View Answer
Explanation: The replica is first written in RAM_DISK and then it is lazily persisted in DISK.
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