What is an SSD?
SSD stands for solid-state drive. An SSD is a type of computer storage device that uses flash memory to store data, rather than mechanical platters and a moving read/write head like a traditional hard disk drive (HDD) (PCMag).
Unlike an HDD, an SSD has no moving parts. Data is stored in microchips rather than on spinning disks coated with magnetic material. This allows SSDs to access data much faster than HDDs, with lower latency and access times. SSDs are also lighter and operate silently with less heat output (PCMag).
Because there are no moving parts, SSDs are less prone to mechanical failures and damage from physical shocks. They are ideal for laptops, tablets, and other mobile devices where durability and performance are desirable.
However, SSDs are typically more expensive per gigabyte than HDDs and have lower storage densities. HDDs remain popular for applications requiring high storage capacity like desktop computers, servers, and data centers.
What is block storage?
Block storage is a technology used for data storage in storage area networks (SANs) or cloud environments. It breaks up data files into evenly sized blocks or chunks of data, each with a unique identifier, so they can be accessed independently (IBM, 2022).
These blocks are then stored on storage media such as hard disks, solid state disks (SSDs), or cloud storage. Each block can be managed and accessed independently from the other blocks. This makes block storage very fast and efficient for accessing specific data since only the relevant blocks need to be read or written (AWS, 2022).
Block storage is considered raw storage as there is no file system or structure imposed on the storage. It is up to the operating system using the storage to organize the blocks into files and folders. This makes block storage very versatile as it can be used for different applications and operating systems (IBM, 2022).
SSD Architecture
SSDs store data on NAND flash memory chips rather than magnetic platters like traditional hard disk drives (HDDs). The architecture of an SSD consists of a controller that manages a set of NAND flash packages. Each NAND flash package contains multiple NAND flash dies, with each die containing thousands of NAND flash memory cells arranged in blocks and pages (SsD – architecture + urbanism).
At the hardware level, data is stored in the flash memory cells as charge on a floating gate transistor. A NAND flash cell can be programmed to store charge representing a binary 1 or 0. Pages contain a set number of bytes, usually 4-16KB, and represent the smallest unit that can be read or written. Blocks contain a set number of pages, usually 64-256 pages, and represent the smallest unit that can be erased (Solid State Drive Architecture).
To store data, the SSD controller receives read/write commands and manages the process of programming pages and erasing blocks across the flash dies. The controller utilizes logic like wear leveling algorithms to distribute writes evenly and maximize lifespan. To access data, the requested page(s) are read from the flash memory into an internal cache on the controller before sending to the host. SSDs appear as block devices to the host system while intelligently managing the underlying flash memory.
Why SSDs are considered block storage
SSDs or solid-state drives meet the criteria that define block storage devices in several key ways:
Access to data happens in fixed size blocks: Like other block storage, SSDs allow access and management of data in blocks of a fixed size, typically 512 bytes to 4,096 bytes. The SSD controller reads and writes data in these blocks.
Data is addressed by block location: SSDs use logical block addressing (LBA) to identify and access data by its block location on the drive. The operating system keeps a mapping table to locate blocks.
Designed for sequential and random access: SSDs support both sequential and random access read/write patterns, a hallmark of block storage. This makes them suitable for both accessing large files as well as small chunks of data.
Supports queuing operations: The SSD controller has native command queuing to reorder read/write commands for optimal performance, another key block storage feature.
With these qualities, SSDs offer the block-level storage capabilities that provide predictable performance, simplified data management, and efficient access controls like traditional hard drives.
Benefits of SSD as block storage
SSDs provide significant benefits as block storage compared to traditional hard disk drives (HDDs). The main advantages are faster access speeds and better overall performance.
SSDs access data almost instantly, with typical read speeds of 500 MB/s or more compared to HDDs which are generally less than 200 MB/s (https://aws.amazon.com/what-is/block-storage/). This is because SSDs use NAND flash memory chips rather than spinning mechanical platters. There are no moving parts to wait for.
In addition, SSDs offer lower latency of just a few microseconds versus HDDs which can be 10-15+ milliseconds. This is crucial for applications that demand fast response times. SSDs can handle many more input/output operations per second (IOPS) which improves throughput.
With their superior speed and responsiveness, SSD block storage delivers better performance for databases, virtual machines, servers and other high transaction environments. Web apps, gaming, analytics and other data-driven applications also benefit greatly from SSDs over HDDs as block storage.
Limitations of SSD as Block Storage
While SSDs offer significant advantages over traditional HDDs for block storage, they also come with some limitations in certain areas:
Cost – SSDs are generally more expensive per gigabyte compared to HDDs. As of 2022, SSD pricing can be 2-4x higher for an equivalent capacity drive (according to Google Cloud). This makes SSD block storage considerably more expensive, especially at scale.
Capacity – HDDs typically offer much higher maximum capacities, with modern HDDs reaching up to 16TB per drive. SSD capacities max out around 30TB currently, though most enterprise SSDs are lower. This can restrict use cases needing massive storage pools (according to Amazon AWS).
Write Endurance – HDDs can be rewritten continuously, while SSDs wear out after substantial rewrites to any given block. Consumer SSDs often have write endurance ratings of a few hundred terabytes. Enterprise models offer higher ratings but still wear out eventually (according to Google Cloud).
Use cases for SSD block storage
SSD block storage shines for applications that require high performance and low latency. Some key use cases where SSDs are preferred over HDD block storage include:
High-performance databases and transactional workloads – The fast random I/O capabilities of SSDs make them ideal for databases like MySQL, PostgreSQL, MongoDB, etc that need to service many concurrent transactions with low latency (1).
Virtual desktop infrastructure (VDI) – The boot storm that occurs when many virtual desktops start up simultaneously strains HDD storage. SSDs handle these workloads easily while providing a snappy user experience (2).
Server boot volumes – Using SSDs for server boot volumes drastically reduces server boot up times compared to HDDs.
Low latency processing – Applications like algorithmic trading, ad serving, etc that are sensitive to microsecond latency spikes benefit from the consistent low latency of SSD block storage.
Frequent read/write workloads – The higher IOPS capabilities of SSDs make them suitable for workloads involving frequent reads and writes like transcoding media files, building code, streaming, etc.
In summary, choosing SSD over HDD block storage provides benefits like faster random reads/writes, lower latency, higher IOPS and throughput for applications where performance matters most.
SSD vs HDD for Block Storage
SSDs and HDDs are both viable options for block storage, but they have key differences that make each better suited for certain use cases. SSDs store data on flash memory chips rather than magnetic platters like HDDs. This gives SSDs significant advantages in performance:
- Higher read/write speeds – SSDs have much faster access times and data transfer rates, especially for random I/O. Typical SSDs can reach over 500MB/s sequential reads while HDDs max out around 200MB/s.
- Lower latency – The lack of moving parts in SSDs reduces seek time to near zero. HDDs require physical movement of the disk head, adding latency.
- Better reliability – With no moving parts, SSDs are less prone to mechanical failure over time.
However, HDDs tend to have higher storage capacities and lower costs per gigabyte. HDDs are better suited for sequential data access, like media storage and backups. SSDs provide major performance benefits for applications requiring high IOPS, like databases, gaming, and operating systems.
When evaluating block storage, SSDs offer faster performance while HDDs offer larger capacities for lower cost. Determining workload patterns and performance needs is key to choosing the right block storage type.
Trends in SSD Block Storage
There are several emerging SSD technologies that are shaping current trends in block storage. According to Gartner, new SSD technologies like Storage Class Memory (SCM) and Computational Storage Drives (CSDs) will gain increased adoption for enterprise workloads over the next few years (source). SCM offers near-DRAM performance at lower cost for ultra-fast storage, while CSDs embed processing capabilities directly into SSDs to enable greater efficiency.
Another key trend is the continuing rise in adoption of flash-based SSDs for block storage use cases. SSDs are displacing traditional hard disk drives (HDDs) for block storage at a rapid pace due to the performance and reliability benefits of flash memory. According to research from ISP.Today, SSDs made up around 40% of capacity shipments for enterprise block storage arrays in 2022, up from just 15% in 2017 (source). This shift towards all-flash arrays is expected to accelerate in the coming years.
NVMe and PCIe Gen 4/5 are also emerging interface standards that allow SSDs to fully leverage the speed of flash memory and reduce latency. These new interfaces combined with optimizations like composable storage architecture point to a future of software-defined, hyperconverged block storage built on commodity SSD hardware.
Conclusion
In summary, SSDs or solid-state drives are a type of block storage device that uses flash memory to store data persistently. SSDs connect to a computer through a host bus interface like SATA or PCIe to provide random access block-level storage for the operating system, applications, and files.
The key architecture of an SSD is a controller that manages multiple NAND flash memory chips, arranging them in channels, packages, and dies to optimize performance. This design provides the benefits of an SSD as block storage such as faster read/write speeds, lower latency, and higher IOPS compared to hard disk drives.
SSDs excel as a block storage solution for use cases that require high performance like databases, gaming PCs, video editing workstations, and enterprise servers. However, limitations like higher cost per gigabyte, finite program-erase cycles, and data recovery challenges in failed drives make HDDs better suited for secondary bulk storage.
Overall, the evolution of NAND flash technology and SSD controllers continue to advance SSD capabilities as block storage. With their fundamental advantages as solid-state devices, SSDs will likely continue displacing HDDs for an increasing proportion of block storage use cases moving forward.