Tuesday, October 30, 2018

hard drive - Latency of SSDs versus HDDs


We are currently using an HDD for our NetApp storage for our VMs. We're considering replacing them with SSDs, but many disk manufacturers have different performance. What range of latencies can we expect from SSDs versus HDDs? How much better are SSDs on average?


Answer



The latencies of an SSD vary hugely, but in terms of IOPs (which us probably the term you want to google)you are looking at an increase in the order of 2-5 magnitudes. (Ie 100 iops for HDD, starting at more then 10000 + for an SSD).


Have a look at https://en.m.wikipedia.org/wiki/IOPS


SSDs are like a night and day difference. I would only use hdds for backups and unimportant archival data - like videos, music collections. A heavily swapping HDD can render a system unuseable - while it will just be a bit sluggish on SSD.


Speedwise SSDs are at least 5 times as fast in sequential reads and writes - which represents the closest benchmark


You did not ask, but SSD is also over 5 times as reliable as hdd (but unlike hdd more likely to fail completely and without warning - so RAID is still important)


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