I am going to write a series of Blogs on Storage Technologies.
This is going to be the introduction to Disk-Level Storage and Storage technologies and its terminology. We will be discussing basic disk and storage architectures as well as storage protocols and common fault tolerance technologies.
Let’s get started with Part-1 i.e., DISKS.
Disks are basic storage units which hold the data. All kinds of disks or disk drives offer the ability to store data. Disks allow storing data from a BYTE to large amounts. Everything stored on disk drives will be persistent. Still, there are major differences in the way the data is actually accessed and stored on different types/generations of disks.
A memory access pattern or IO access pattern is the pattern with which a system or program reads and writes memory or secondary storage. There are two types of Access Patterns
- Sequential Access Pattern
- Random Access Pattern.
Below image best describes the Access Patterns
Let’s see the type of disks and their pros and cons.
Hard Disk Drives
Hard disk drives or HDDs are the traditional types of disk drives. These kinds of disks consist of rotating rigid platters on a motor-driven spindle. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the platters. Data is accessed with Random Access Pattern. Cost per GB is very less. Consumes more energy.
Solid State Disks (SSDs)
In contrast to HDDs, SSDs use microchips which retain data in non-volatile memory chips (flash) and contain no rotating or moving parts within. As compared to HDDs, SSDs are silent, have lower access time and latency (typically <1ms), and have higher I/O rates (typically >3.000), but are more expensive per GB and typically support a limited number of writes over the life of the device. SSDs use the same interface as hard disk drives, thus easily replacing them in most applications. Consumes very less energy compared to HDDs and SSDs are shockproof.
Performance comparison between HDDs and SSDs
SSDs performance varies with available storage. If SDD is full then you would see some degradation in performance.
|Performance comparison between HDDs and SSDs|
|PARAMETER||Hard Disk Drives (HDDs)||Solid State Drives (SSDs)|
|Read IO (Random)||Slow||Very Fast|
|Read (Sequential)||Fast||Very Fast|
|Write IO (Random)||Slow||Very Fast|
|Write ( Sequential)||Fast||Very Fast|
|Read Write (Mixed)||Fast||Fast|