Tips for Selecting SSD and HDDs
are a number of factors to be considered when selecting drives for a storage
environment. These include the level of sequential or random access performance
needed, storage density, reliability and cost. With today's wide variety of
storage devices, many IT professionals are challenged with the multitudes of
drive technologies. This is especially true when selecting the appropriate
drives for various data types. Adding to the confusion is that SATA and SAS
refer to disk drive interfaces, whereas SSD refers to a particular kind of
internal technology. Selecting a drive technology and interface type can seem
complex with considerations of random access performance, sequential
performance, cost, density and reliability, but is manageable with the right
By observing the following tips on drive
selection, confusion over drive choice can be significantly reduced.
Do not confuse disk interface type with
performance or reliability
Historically, SAS and SATA were used as convenient
shorthand for fast or dense disk drives, respectively. Now, however, there are
SSD drives with SATA interfaces as well as inexpensive and dense but relatively
low-IOPS 7200 RPM drives with SAS or even FC interfaces.
Achieve the best price/GB with 3.5" 7200 RPM
vendors have a seemingly endless variety of pricing models, but one constant
seems to be that 2.5" systems cost twice as much per gigabyte as 3.5" systems,
assuming both are using 'enterprise-grade' drives. But as noted previously, a
3.5" drive will be far more reliable.
Understand that HDD performance is mostly
dictated by density and mechanical speed
The random or transactional (IOPS) performance of spinning
drives is dominated by the access time, which in turn, is determined by
rotational latency and seek time. Interface performance has almost no impact on
IOPS. Additionally, interface speed has no measurable impact on sustained
Consider SSD drives instead of 10K or 15K drives for
Today it is very likely that an all-SSD storage solution will have lower overall
capital and operational cost than one made from 15,000 RPM drives due to the
reduction in total slots required to achieve a given transaction performance.
Additionally, SSDs have a greatly reduced power footprint compared to spinning
drives for a given number of transactions.
When building systems with high sequential
performance for applications such as video, 3TB 7200 RPM SATA drives are better
than SSD or 10K/15K drives
Somewhat surprisingly, neither SSDs nor 10,000/15,000 RPM
disk drives are better for video and other streaming media applications than
7200 RPM SATA drives, unless there are numerous independent streams being
written or read from the same RAID set.
Hardware matters, and organizations intent on maintaining a robust storage
environment should not underestimate the importance of optimizing storage
infrastructure with quality hardware components and technology that is aligned
with the operating environment. Correct drive choice plays a major role in
the overall reliability and performance of a storage system