Distributed file systems in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main component responsible for storing file metadata in a distributed file system.

HLD

The component that stores file metadata in a distributed file system is called the [1].

Drag options to blanks, or click blank then click option'

AName Node

BData Node

CClient Node

DCache Server

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing Data Node with Name Node

Thinking Client Node stores metadata

The Name Node manages metadata like file names, directories, and block locations in distributed file systems such as HDFS.

2fill in blank

medium

Complete the code to specify the protocol used by clients to communicate with data nodes in a distributed file system.

HLD

Clients communicate with data nodes using the [1] protocol.

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ARemote Procedure Call (RPC)

BSMTP

CHTTP

DFTP

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing HTTP or FTP which are not typical for data node communication

Confusing SMTP with communication protocol here

RPC is commonly used for communication between clients and data nodes in distributed file systems for efficient remote method invocation.

3fill in blank

hard

Fix the error in the description of data replication in distributed file systems.

HLD

Data replication ensures that each data block is stored on [1] different nodes to provide fault tolerance.

Drag options to blanks, or click blank then click option'

Atwo

Bthree

Cone

Dfour

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing one or two which is insufficient for fault tolerance

Choosing four which is more than typical default replication

Typically, distributed file systems replicate data blocks on three different nodes to balance fault tolerance and storage overhead.

4fill in blank

hard

Fill both blanks to complete the description of the request flow in a distributed file system.

HLD

When a client wants to read a file, it first contacts the [1] to get the [2] of the data blocks.

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AName Node

BData Node

Clocations

Dmetadata

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing Data Node as the first contact

Mixing metadata with locations in the second blank

The client contacts the Name Node to get the locations of data blocks before reading from Data Nodes.

5fill in blank

hard

Fill all three blanks to complete the description of fault tolerance mechanisms in distributed file systems.

HLD

To handle node failures, the system uses [1] to replicate data, [2] to detect failures, and [3] to reassign tasks.

Drag options to blanks, or click blank then click option'

Areplication

Bheartbeat

Cfailover

Dcaching

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing caching with replication

Not understanding heartbeat's role in failure detection

Replication copies data, heartbeat signals detect node failures, and failover reassigns tasks to healthy nodes.

Practice

1. What is the main role of a metadata server in a distributed file system?

easy

A. To keep track of file locations and directory structure

B. To store the actual file data

C. To provide network connectivity between clients

D. To encrypt files before storage

Solution

1. Step 1: Understand metadata server function

   The metadata server manages information about where files are stored and their organization.

2. Step 2: Differentiate from storage nodes

   Storage nodes hold the actual file data, not metadata servers.

3. Final Answer:

   To keep track of file locations and directory structure -> Option A

4. Quick Check:

   Metadata server = file info tracker [OK]

Hint: Metadata servers track file info, not data storage [OK]

Common Mistakes:

• Confusing metadata server with storage node
• Thinking metadata server stores file data
• Assuming metadata server handles encryption

2. Which of the following is the correct sequence when a client reads a file in a distributed file system?

easy

A. Client contacts only the storage node

B. Client contacts storage node, then metadata server

C. Client contacts only the metadata server

D. Client contacts metadata server, then storage node

Solution

1. Step 1: Identify client interaction flow

   The client first asks the metadata server for file location details.

2. Step 2: Access data from storage node

   After getting location info, the client reads the actual file data from the storage node.

3. Final Answer:

   Client contacts metadata server, then storage node -> Option D

4. Quick Check:

   Read flow = metadata server then storage node [OK]

Hint: Client asks metadata first, then reads data [OK]

Common Mistakes:

• Reversing the order of contacting servers
• Assuming client contacts only one server type
• Ignoring metadata server role in locating files

3. Consider a distributed file system where a file is split into 3 chunks stored on different storage nodes. If the metadata server returns chunk locations as [Node1, Node2, Node3], what happens when the client requests the file?

medium

A. Client reads all chunks sequentially from Node1 only

B. Client reads chunks in parallel from Node1, Node2, and Node3

C. Client reads chunks randomly from any node

D. Client reads only the first chunk from Node1

Solution

1. Step 1: Understand chunk distribution

   The file is divided into chunks stored on separate nodes for parallel access.

2. Step 2: Client reads chunks efficiently

   To speed up reading, the client fetches all chunks at the same time from their respective nodes.

3. Final Answer:

   Client reads chunks in parallel from Node1, Node2, and Node3 -> Option B

4. Quick Check:

   Parallel chunk reads = faster file access [OK]

Hint: Chunks read in parallel from all nodes [OK]

Common Mistakes:

• Assuming client reads all chunks from one node
• Thinking chunks are read randomly
• Ignoring parallelism benefits

4. A distributed file system client tries to read a file but gets an error because the metadata server is unreachable. What is the most likely cause?

medium

A. Client has no network access to metadata server

B. Storage nodes are down

C. File data is corrupted on storage nodes

D. Client requested a non-existent file chunk

Solution

1. Step 1: Identify error source

   The error is due to inability to reach the metadata server, not storage nodes.

2. Step 2: Analyze network access

   Most likely, the client cannot connect to the metadata server because of network issues or firewall rules.

3. Final Answer:

   Client has no network access to metadata server -> Option A

4. Quick Check:

   Metadata server unreachable = network issue [OK]

Hint: Metadata server unreachable means network problem [OK]

Common Mistakes:

• Blaming storage nodes for metadata server errors
• Assuming file corruption causes metadata errors
• Confusing chunk existence with server reachability

5. You are designing a distributed file system for a company with many users reading large files frequently but rarely writing. Which design choice improves read performance the most?

hard

A. Disable caching to ensure fresh data on every read

B. Store all file chunks on a single storage node to simplify access

C. Use multiple metadata servers with caching to reduce lookup latency

D. Limit the number of storage nodes to reduce network overhead

Solution

1. Step 1: Analyze workload pattern

   Many reads and few writes mean caching metadata can speed up file location lookups.

2. Step 2: Evaluate design options

   Multiple metadata servers with caching reduce latency and avoid bottlenecks, improving read speed.

3. Step 3: Reject other options

   Storing all chunks on one node limits scalability; disabling caching slows reads; fewer nodes reduce parallelism.

4. Final Answer:

   Use multiple metadata servers with caching to reduce lookup latency -> Option C

5. Quick Check:

   Metadata caching + multiple servers = faster reads [OK]

Hint: Cache metadata and use multiple servers for fast reads [OK]

Common Mistakes:

• Putting all data on one node limits scalability
• Disabling caching hurts read performance
• Reducing nodes lowers parallel access