Storage
Solid State Drive (SSD)
- technology
- flash memory
- internal interfaces
- PCIe/NVMe, SATA/AHCI (legacy)
- packaging
- 2.5", M.2, U.2, PCIe card, BGA (soldered)
- performance
- sequential read/write up to 15 GB/s (single drive)
- latency down to tens to hundreds of μs (depending on conditions)
- power consumption typically a few W, lower at idle
- true random access
- slower when nearly full
- limited data retention time
- rugged and reliable
- external drives
- USB interface
- large range of performance
- uses
- system drives, portable devices, high-speed storage, data transfer
Hard Disk Drive (HDD)
- technology
- rotating platters with magnetic coating
- one read/write head per surface, moved by voice coil
- interfaces
- SATA/AHCI or SAS
- packaging
- 3.5", 2.5"
- performance
- sequential read/write up to 200 MB/s
- latency on the order of 10 ms (seek to desired track and rotation to desired sector)
- power consumption typically tens of W
- slower when fragmented
- enterprise grade fairly reliable, consumer grade much less
- sensitive to shock, vibration, temperature extremes
- uses
- bulk storage, offline storage, backup
- lower cost than SSD
Optical Disc Drive (ODD)
- technology
- removable rotating transparent platter
- information contained in thin metal (read-only) or dye (read-write) layer(s)
- moving head with laser
- interfaces
- SATA/AHCI, USB
- packaging
- 5.25"
- types
- CD stores 650 MB to 700 MB
- DVD stores 4.7 GB or 9.4 GB
- Blu-Ray stores 25 GB to 128 GB
- performance
- sequential read/write up to 72 MB/s
- serial access (huge latency)
- power consumption tens of W
- moderate reliability, but M-Disc media have high reliability
- sensitive to shock, vibration, temperature extremes
- uses
- entertainment, software distribution, archiving
- legacy product
LTO (Linear Tape Open) ☠
- technology
- thin plastic tape with a magnetic coating wound on reels in removable cassettes
- tape pulled past fixed head
- interfaces
- SAS
- packaging
- 5.25", external
- cartridge capacity
- LTO-10 30 TB (uncompressed)
- performance
- sequential read/write up to 400 MB/s
- serial access (huge latency)
- low reliability
- limited data retention
- sensitive to shock, vibration, temperature extremes, humidity, dust (i.e. everything)
- power consumption tens of W
- expensive drives, low media cost
- uses
- backup
UNIX considerations
- amount
- a lightweight, character only distro might install in less than 1 GB
- a minimal GUI distro will need 8 GB or more
- a full-featured GUI distro will need 32 GB or more
- additional desktop requirements depend on applications
- additional server requirements depend on services and load
- extra storage improves performance, SSD life, and flexibility
- multiple devices
- recommended for servers, routers, other situations which require high reliability and availability