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Solid-state drive

솔리드 스테이트 드라이브(solid-state drive, SSD) 또는 솔리드 스테이트 디스크(solid state disk)는 반도체를 이용하여 정보를 저장하는 장치이다.

솔리드 스테이트 드라이브는 순수 전자식으로 작동하므로 기계식인 하드 디스크 드라이브(HDD)의 문제인 긴 탐색 시간, 반응 시간, 기계적 지연, 실패율, 소음을 크게 줄여 준다. 반면에 DRAM이 아닌 플래시 메모리가 적용된 SSD의 경우, 데이터 접근 시간이 아닌 연속적인 읽기와 쓰기에 대해 하드 디스크보다 속도가 낮은 경우가 대부분이었다. 하지만 최신 기술이 적용된 SSD의 경우, 대부분 하드 디스크 드라이브 이상의 읽기와 쓰기 속도를 낸다.

File system support for SSDs

Typically the same file systems used on hard disk drives can also be used on solid state drives. It is usually expected for the file system to support the TRIM command which helps the SSD to recycle discarded data (support for TRIM arrived some years after SSDs themselves but is now nearly universal). This means that file system does not need to manage wear leveling or other flash memory characteristics, as they are handled internally by the SSD. Some flash file systems using log-based designs (F2FS, JFFS2) help to reduce write amplification on SSDs, especially in situations where only very small amounts of data are changed, such as when updating file-system metadata.

While not a file system feature, operating systems should also aim to align partitions correctly, which avoids excessive read-modify-write cycles. A typical practice for personal computers is to have each partition aligned to start at a 1 MiB (= 1,048,576 bytes) mark, which covers all common SSD page and block size scenarios, as it is divisible by all commonly used sizes - 1 MiB, 512 KiB, 128 KiB, 4 KiB, and 512 B. Modern operating system installation software and disk tools handle this automatically.

Optimization

See also

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References

  1. Coding_for_SSD_-_Part_1.pdf ↩

  2. Coding_for_SSD_-_Part_2.pdf ↩

  3. Coding_for_SSD_-_Part_3.pdf ↩

  4. Coding_for_SSD_-_Part_4.pdf ↩

  5. Coding_for_SSD_-_Part_5.pdf ↩

  6. Coding_for_SSD_-_Part_6.pdf ↩