Block Storage is a data storage model where data is stored and accessed as fixed-size blocks, each with its own unique address, and presented to an operating system as a raw disk device.
From the OS and application perspective, block storage behaves like a local hard drive, even though it may be physically located on a separate storage system and accessed over a network.
How Block Storage Works?
In block storage:
- Data is divided into blocks of equal size
- Each block is addressed independently
- The storage system does not understand files or directories
- File systems, databases, or applications manage their structure themselves
This low-level access provides maximum flexibility and performance.
Block Storage vs File Storage vs Object Storage
| Aspect | Block Storage | File Storage | Object Storage |
| Data access | Raw blocks | Files/directories | Objects |
| OS view | Disk device | Mounted filesystem | API-based |
| Latency | Low | Medium | Higher |
| Use cases | Databases, VMs | Shared files | Archives, media |
| Structure | Client-managed | Storage-managed | Metadata-driven |
Block storage is chosen when performance and control are critical.
Key Characteristics of Block Storage
1. Low Latency and High IOPS
Direct block access enables fast read/write operations, essential for transactional workloads.
2. Consistent Performance
Predictable behavior under load, especially when backed by enterprise SSDs or NVMe devices.
3. Flexible File Systems
Clients can use any file system or raw access:
- ext4, XFS, ZFS
- NTFS
- Database-managed storage
4. Isolation
Each block device is typically assigned to a single server or VM, reducing contention.
Block Storage in Cloud and Private Cloud
In Private Cloud environments:
- Block storage is often provided via:
- SAN (iSCSI, Fibre Channel)
- Software-defined storage (Ceph, OpenStack Cinder)
- Volumes can be:
- Attached
- Detached
- Resized
- Migrated
Block storage is the foundation for virtual machine disks and many container platforms.
Reliability and Redundancy
Enterprise block storage systems include:
- Data replication
- RAID or erasure coding
- Automatic failover
- Snapshot capabilities
However, redundancy does not replace backups.
Block Storage and Performance Planning
Performance depends on:
- Storage backend (SSD, NVMe, HDD)
- Network latency and bandwidth
- Queue depth and I/O patterns
- Replication and consistency settings
Block storage must be designed, not just allocated.
What Block Storage Is Not?
❌ Not a shared filesystem
❌ Not object storage
❌ Not inherently scalable without architecture
❌ Not automatically protected from data corruption
❌ Not a substitute for backups
Incorrect use of block storage often leads to data loss or performance bottlenecks.
Typical Use Cases
Block storage is ideal for:
- Databases (SQL, NoSQL)
- Virtual machine disks
- High-performance applications
- Transactional systems
- Stateful services in Private Cloud.
Business Value of Block Storage
For clients:
- High and predictable performance
- Full control over data layout
- Compatibility with enterprise workloads
- Scalability through design, not abstraction
For us:
- A core building block of Private Cloud and complex storage solutions
- A component that must be integrated with the network, compute, and backup strategy
Our Approach to Block Storage
We treat block storage as:
- A low-level infrastructure primitive
- A performance-critical component
- A responsibility that includes design, monitoring, and recovery planning.