There are several methods available to access data stored on a computer or other digital device. The method used depends on factors like where the data is stored, what kind of data it is, and how the user needs to interact with it. Some common methods for accessing stored data include:
File Access
Files stored on a hard drive or solid state drive can be accessed directly through the device’s file system. This involves using a file manager or explorer tool to navigate folder directories and open files. Common tools for file access include Windows Explorer, Mac Finder, Linux file managers, and mobile device file browsers. Files can be viewed, edited, copied, moved, and deleted through these file manager programs.
Database Access
Data stored in databases requires database management software to access it. These programs allow users to connect to a database, submit queries to retrieve data, and manipulate data. SQL is a common database query language used by software like MySQL, Oracle, SQL Server, and Access. APIs and object-relational mapping tools also facilitate database access in many programming languages.
Network Access
Data stored on networked devices and servers can be accessed over a local network or the internet. Protocols like SMB/CIFS allow file access across Windows networks. NFS does the same for Unix-like networks. Secure shell and remote desktop protocols enable accessing remote command lines and full desktop environments. Web APIs power data access through web-based services.
Cloud Storage Access
Major cloud storage providers like Amazon AWS, Microsoft Azure, and Google Cloud Platform allow access to data stored in the cloud through web APIs and purpose-built client libraries. Developer tools let applications integrate cloud storage like S3 buckets, Blob containers, and Firebase Storage. Many also provide file system interfaces like EBS and Google Drive for more user-friendly access.
Memory Access
Running applications and processes store data temporarily in a device’s RAM and cache memory as they run. This data can be accessed through the /proc file system in Unix-like systems or memory dump tools like ProcDump for Windows. Debuggers and profilers allow finer-grained memory access for application debugging and optimization.
Virtual Machine Access
Virtual machine hypervisors make data stored within virtual disk images accessible from the host and client OSs. VMs like VirtualBox, VMware, Hyper-V, and QEMU implement virtual disk support through VMDK, VHD, and other disk image formats. These present guest data as local disk drives to the virtual OS.
Block Storage Access
Block storage divides data storage into fixed-size blocks. These blocks act as virtual disk partitions that can be accessed like regular drives. SAN and NAS devices provide block storage access over a network. Cloud block storage like AWS EBS and Azure Disk Storage present iSCSI disks to cloud compute instances.
Object Storage Access
Object storage manages data as distinct objects instead of files or blocks. Object storage systems like Ceph, Minio, and Cloudian allow accessing these objects through REST APIs or S3-compatible gateways. Object data can also be streamed in some cases.
Archival & Backup Access
Archival data written to long-term cold storage like tapes and optical discs must be restored to online storage before accessing normally. Backups similarly require restoring from backup media. Purpose-built utilities then allow browsing and restoring archived and backed-up files as needed.
Specialized Storage Access
Some storage technologies require special methods for data access. For example, in-memory databases store data in RAM for faster access. Non-volatile DIMMs combine RAM and flash storage. Accessing data on DNA or film drives requires special equipment. Hardware security modules securely store and control access to sensitive data like cryptographic keys.
Choosing an Access Method
The best method for accessing stored data depends on several factors:
- Location – Local vs networked vs cloud vs offline storage
- Data structures – Blocks vs files vs objects vs databases
- Protocols – Filesystems vs block storage protocols vs S3 vs databases
- Tools available – APIs, libraries, utilities, interfaces
- Security needs – Authentication, encryption, air gaping
- Performance needs – Speed, caching, queries
- Access frequency – Online vs archival or backup
Understanding both the nature of the stored data and access requirements is necessary to select the optimal method. Using inappropriate methods can hinder performance, reliability, and security.
Common Situations and Solutions
| Situation | Recommended Access Method |
|---|---|
| Application needs fast startup data | In-memory database or cache |
| App stores structured data | Local database like SQLite + ORM |
| User documents and media | Local filesystem via file manager |
| Shared files across a workgroup | Network filesystem like SMB/CIFS |
| Development and test virtual machines | Virtual machine hypervisor |
| Cloud-native app data | Cloud object storage with REST API |
| Backing up user laptop | External drive or cloud backup solution |
| Big data analytics | Distributed filesystem like HDFS |
Key Considerations
Some key considerations when determining data access methods:
- Speed – Some methods access data faster than others (e.g. in-memory vs disks)
- Concurrency – How simultaneous access handled, if needed
- Capacity – Total storage size limits
- Reliability – Frequency and impact of data loss/corruption
- Durability – Lifespan of stored data
- Interfaces – APIs, libraries, tools available
- Searching – Query, indexing, and filtering capabilities
- Location – Physical location of stored data
- Mobility – Ability to move or replicate data
- Security – Authentication, encryption, and access control
The strengths and weaknesses of each access method in these areas should align with application requirements.
Examples of Access Methods
Some examples of data access methods for different scenarios:
Mobile App Local Data
A mobile app that collects user data like settings, documents, and cache files. This data is best stored locally using:
- SQLite database for structured app data
- Local filesystem for docs and media
- SharedPreferences or SQLite for settings
Multi-user Web App
A web app allowing thousands of users to store data in the cloud requires:
- Cloud SQL or NoSQL database
- Cloud object storage like S3
- REST APIs and SDKs for data access
- Relational models and query languages
- Caching layers like Redis
Data Warehousing
Analyzing large volumes of structured business data benefits from:
- Columnar database like Vertica or ClickHouse
- Alternative storage like ORC and Parquet formats
- Distributed filesystem like HDFS
- MapReduce, Spark, or SQL access and queries
Backing Up Servers
Reliably backing up remote Linux servers requires:
- Network filesystem like NFS for mounting storage
- rsync for efficient incremental backup
- SSH for secure remote access
- Deduplication to reduce storage needs
Conclusion
There are many ways to access data stored digitally, each with their own strengths and use cases. Key criteria like speed, interfaces, location, structure, and security guide the selection process. Common methods include filesystems, databases, networks, clouds, and virtualized access. With careful matching of access methods to requirements, applications can efficiently leverage the wide array of data storage technologies available.