Choosing the Right Cloud Storage: NAS, Block, and Object Explained

Introduction

The article introduces common storage types and their differences, helping readers choose the appropriate storage for various requirements and scenarios.

Physical Storage Layer

Storage at the physical layer is essentially a disk (magnetic recording technology). Early computers used floppy disks; modern systems mainly use hard disks.

Disk Metrics

Three key indicators for disks are throughput, IOPS, and latency. The relationship can be expressed as: Throughput per second = I/O size × IOPS × parallelism.

Throughput : amount of data successfully transferred per unit time.

IOPS : Input/Output Operations Per Second, measuring read/write operations per second.

Latency : time interval between issuing a read request and receiving the data.

Alibaba Cloud Storage Architecture

Alibaba Cloud virtualizes physical disk resources into a pooled storage system managed by the distributed Pangu scheduler, offering on‑demand, pay‑as‑you‑go usage similar to utilities.

Storage Type Differences

File, block, and object storage represent three ways to organize and present data.

File storage (NAS) organizes data in a hierarchical file‑folder structure.

Block storage (EBS) splits data into equal‑sized volumes.

Object storage (OSS) manages data as objects linked to metadata.

Interface and Protocol Differences

Each storage product uses different protocols and access methods.

File storage (NAS) uses NFS or SMB protocols, supporting POSIX interfaces.

Block storage (EBS) uses Alibaba‑developed iSCSI protocol.

Object storage (OSS) uses HTTP/HTTPS (RESTful API) and is compatible with AWS S3.

Application Scenarios

Because of their distinct data structures, the three products suit different workloads.

File Storage (NAS)

Provides directory‑tree architecture, supports thousands of ECS instances accessing concurrently via POSIX, suitable for high‑concurrency, online modification, and direct read/write scenarios.

Block Storage (EBS)

Offers high performance and low latency, ideal for I/O‑intensive workloads such as OLTP databases and NoSQL databases. It must be formatted into a file system before use and does not support elastic capacity expansion beyond 32 TB per volume.

Object Storage (OSS)

Uses a flat S3‑style organization, does not support random file reads, and is best for massive data upload/download and distribution in internet architectures.

Comparison Table

Storage Product

Latency

Throughput

Protocol

Access Mode

Application Scenario

File Storage NAS

Millisecond‑level

Hundreds of Gbps

NFS, SMB

Thousands of ECS instances via POSIX, random read/write

High‑concurrency, online modification, direct read/write

Object Storage OSS

Dozens of milliseconds

Hundreds of Gbps

HTTP, HTTPS (RESTful API)

Millions of clients via web, append‑only writes

Massive data upload/download and distribution

Block Storage EBS

Microsecond‑level

Tens of Gbps

Self‑developed protocol (iSCSI)

Single ECS via POSIX, random read/write

IO‑intensive databases or single‑ECS high‑performance, low‑latency workloads

Protocol Details

NFS Protocol

Network File System, a UNIX presentation‑layer protocol for file sharing. It provides basic file operations and relies on RPC for TCP/IP transport; encryption requires Kerberos.

SMB Protocol

Server Message Block, a network file sharing protocol (CIFS is its derivative). It works across Windows and Linux, but performance may vary on Linux.

iSCSI Protocol

Internet Small Computer System Interface, a storage protocol over TCP/IP (ports 860 and 3260) that transports SCSI commands, enabling SANs to appear as local storage.

POSIX Interface

Portable Operating System Interface defines a set of APIs for portable software across UNIX‑like systems, abstracting system calls.

RESTful API

Design style based on HTTP, using standard methods (GET, POST, PUT, DELETE) to perform CRUD operations on resources.

Protocol Comparison

iSCSI uses TCP/IP ports to exchange SCSI commands; CIFS/SMB operates at a higher layer as an application protocol; NFS enables remote file access as if local.

References

What is RESTful API? https://blog.csdn.net/qq_41378597/article/details/85248848

RESTful Wikipedia https://baike.baidu.com/item/RESTful

NAS – Alibaba Cloud Documentation https://help.aliyun.com/product/27516.html

POSIX – What is it and what problems does it solve? https://blog.csdn.net/sir_chai/article/details/105652646