SSD vs. HDD: Speed

What makes SSDs an increasingly popular choice is their speed. Across the board, SSDs outpace HDDs because they use electrical circuitry and have no physical moving parts. This leads to shorter wait times when you’re starting up and fewer delays when opening apps or doing heavy computing tasks. For example, the Intel SSD D5-P5316 is a 15.36TB enterprise-grade SSD that offers over 7000 MB/s in bandwidth. The 14TB Seagate Exos 2x14, a compatible HDD, offers only up to 500 MB/s in bandwidth. That’s a difference of 14x!

SSD vs. HDD: Endurance

The degree of write wear to a NAND SSD depends partly on the state of data already on the drive, because data is written in pages but erased in blocks. When writing sequential data to a relatively new SSD, data can be efficiently written to successive, free pages on the drive. However, when small blocks of data need to be updated (as in revising documents or numerical values), the old data is read into memory, revised, and then re-written to a new page on the disk. The old page, containing deprecated data, is marked invalid. When free pages are no longer available, those “invalid” pages are freed up for use in a background process called “defragmentation” or “wear leveling.” All existing valid pages in a given block must first be copied to other free locations on the drive so that the original block only contains invalid, deprecated pages. The original block can then be erased to free up space for new data to be written.

Head-to-Head Comparison: SSD vs. HDD

When it comes to capacity, SSDs for computers are available in 120GB to 30.72TB capacities, whereas HDDs can go anywhere from 250GB to 20TB. When measuring cost per capacity, HDDs come out on top, but as SSDs drop in price, this will become less of a differentiator for HDDs. However, with SSDs, you get much more work done per server which results in fewer devices deployed to get the same output as an HDD. The result? SSDs have a lower TCO (total cost of ownership).

SSD Cost Savings over HDDs

It is well understood that SSDs perform significantly better than HDDs. Almost as well understood is the reliability advantage of SSDs. Given these intrinsic advantages, SSDs do not need replication for performance, and they generally require much less replication for reliability. Higher SSD performance also lends itself to much more efficient data-reduction methods than HDDs. Data reduction is the ratio of host data stored to physical storage required; a 50 percent ratio would be equivalent to a 2:1 data-reduction ratio. Because data reduction allows the user to store more data than is on the physical hardware, the resulting effective capacity is increased. Compression and deduplication technologies can greatly decrease the required raw storage capacity needed to meet a “usable capacity” requirement.