Parallel File System

What is a Parallel File System?

A Parallel File System (PFS) is a high-performance storage system designed to distribute and manage data across multiple storage nodes simultaneously. It enables concurrent read and write access from multiple clients to improve throughput, scalability, and fault tolerance. Parallel file systems are widely used in HPC (High-Performance Computing) environments, where large-scale data processing and efficient I/O operations are crucial.

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Architecture of a Parallel File System

Here’s a basic architecture diagram of a Parallel File System (PFS):

A typical parallel file system consists of the following key components:

1. Clients

• Compute nodes in an HPC cluster that interact with the file system.

• Multiple clients can perform simultaneous read and write operations to the file system.

• Examples: Nodes running MPI applications that need fast access to shared data.

2. Metadata Servers (MDS)

• Manages file metadata (file names, directories, permissions, and file layouts).

• Metadata operations are separated from data access to improve performance.

• Typically, multiple MDSs are used for scalability and fault tolerance.

3. Object Storage Servers (OSS) / I/O Servers

• Store the actual file data across multiple storage nodes.

• Data is striped across multiple storage devices for high bandwidth.

• They serve read/write requests from clients efficiently.

4. Storage Devices (Object Storage Targets - OSTs)

• These are the physical or logical disks that store the data blocks.

• Often implemented using high-speed SSDs, HDDs, or NVMe drives.

• Typically configured in RAID for redundancy and reliability.

5. High-Speed Network (Interconnect)

• Connects clients, metadata servers, and storage servers.

• High-bandwidth and low-latency networks such as InfiniBand, Omni-Path, or high-speed Ethernet are used.

• Optimized for large-scale data transfers.

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Workflow in a Parallel File System

1. File Creation:

   • A client requests the MDS to create a file.

   • The MDS allocates metadata and assigns stripe locations across OSSs.

2. File Access (Read/Write):

   • The client queries the MDS for metadata and storage location.

   • The client directly communicates with OSSs to read/write data (bypassing the MDS).

   • Data is transferred over a high-speed network for maximum efficiency.

3. Load Balancing & Striping:

   • Files are split and distributed across multiple OSSs.

   • This parallel data distribution ensures higher throughput.

4. Fault Tolerance & Redundancy:

   • RAID and data replication mechanisms ensure reliability.

   • If an OSS or storage device fails, data is recovered from redundant copies.

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Popular Parallel File Systems

File System	Features	Used In
Lustre	High scalability, used in Exascale computing	HPC, AI workloads
IBM Spectrum Scale (GPFS)	Supports distributed computing, advanced caching	Enterprise and research clusters
BeeGFS	Easy to set up, good for medium-sized HPC	AI, ML, and HPC workloads
OrangeFS	Open-source, lightweight, optimized for cloud-HPC	Academic and research computing

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Advantages of Parallel File Systems

✅ High Throughput – Multiple nodes can access data in parallel.
✅ Scalability – Designed for thousands of compute nodes.
✅ Reduced Bottlenecks – Separates metadata and data paths.
✅ Fault Tolerance – Redundant storage ensures data safety.
✅ Optimized for HPC & AI – Essential for large-scale simulations, training deep learning models, etc.