Monday, July 11, 2011

Solid State Drives, some theory and a selection of videos

Today I have been looking for information about SSD disks because I am probably interested in using them for my future home-made NAS solution. Having found this SSD topic pretty interesting, I have decided to write a post about it.

Let's start form the acronym: SSD means Solid State Drives, which is a new technology spreading very fast and finally reaching the end-user. In general terms, SSD can be defined as a hybrid device which stores your data (as well as your Operating System, of course) in a semi-conductor device known as flash memory with no mechanical parts (no moving heads or spinning disks).

Thanks to their construction, SSDs have rock solid advantages over standard mechanical hard disk drives. These advantages can be summarized as follow:
  • No spin-up time
  • Extremely low random access time (about 0.1ms)
  • Consistent read time throughout the SSD (while on a HDD if the data is written in a fragmented way, read ops will have varying response times)
  • Zero defragmentation
  • No noise (great for a home NAS)
  • Very light (SSDs size is 2,5" with SATA connectors)
  • Lower power consumption (Excellent for the environment and for your monthly bill)
  • Unaffected by magnetic fields
  • Very robust
As you can see some of this advantages are exactly what can be found on everybody's wishlist for a consumer NAS, that is no noise, low power consumption (for instance only 2,5 watts for the Corsair Force GT 120GB - 0,6 watts when in standby) and really high performances. As an example, let's have a look at some scores:
  • The Intel 510 Series 250 GB is by far the fastest SSD around with 476MB/s read throughput and 325MB/s for write operations. Such speed require SATA III intrerface of course, being SATA II limited to 300MB/s.
  • The Crucial RealSSD M4 256 GB is also a fast model, with 310MB/s for read ops and 273 for write ops.
  • The Plextor PX-128M2S can read at 287MB/s and write at 195MB/s.
  • Other models are a little slower with an average read throughput of 220MB/s and an average write throughput of 155MB/s. These scores are in any case much higher of those of mechanical hard drives, which have a average read throughput of 105MB/s and and an average write throughput of 103MB/s, plus the extra spin-up time.
There are of course some disadvantages in this new technology that SSD designers and constructors are trying to workaround.
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