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why is a Solid State Drive (SSD) faster than a Hard Disk Drive (HDD)?

GMartin
GMartin asked
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Hello and Good Afternoon Everyone,

           I have heard that a Solid State Drive (SSD) is much faster than a Hard Disk Drive (HDD).  With regards to why an SSD is faster than an HDD, I have not really been given any explanations.  That said, does anyone know why an SSD would have better speed performance than an HDD?

           Any shared thoughts to this question will be appreciated.

           Thank you

            George
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Software Engineer
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Commented:
For HDD (spinning disks..., rotating rust etc.) ...  the disk head need to be moved to the right track (seek time) and you may need to wait between 0 & one rotation before the data passes under the heads. ==> on average half a rotational delay. That's why disks in data centers are 15000 RPM (and run a lot hotter, and produce a lot more noise) than laptop disks..   Also the transfer speed is influenced by the rotation speed as the data can be processed faster when there is a higher RPM.

SSD are also callled Zero seek disks. The date can almost immediately be imported/exported on memory transfer speeds.
So (almost) no waiting times with SSD
Bill PrewTest your restores, not your backups...
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Commented:
AA decent summary of the differences here, explains it better than I could...

A Look at the Differences Between SSD and HDD


»bp
Lee W, MVPTechnology and Business Process Advisor
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Commented:
I'll add that there are also two common types of SSDs these days.  Or more technically accurate, two different interfaces for them.  When SSDs first became popular they were attached to SATA buses - the same kind of connection a spinning hard drive uses.  The SATA bus has a limit of about 600 MB/Sec.  Spinning disks can vary with platter density (size), but in my experience, they generally transfer data at about 100-200 MB/Sec.  SSDs on a SATA interface don't have the spinning disk bottleneck to worry about so you can see throughput much closer to the maximum throughput of SATA technology - 500-550 MB/Sec.  But more recently NVMe based drives connect DIRECTLY to the PCIe bus, bypassing the SATA bus.  The limit for these drives is now based on the PCIe bus and the speed of the chips storing the data.  As a result, NVMe drives can operate at speeds up to and even faster than 3000 MB/sec.  

These days, I only use spinning disks for large storage.  My download folder, archives, my collection of videos from Media Center.... my main hard drive is NVMe and my system can boot in 10-15 seconds as opposed to 1-3 minutes with older technology.
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Commented:
and like all ram, SSD data can be accessed at random - so no speed loss there too
more info here :  https://gizmodo.com/intel-invented-the-ssd-killer-of-the-future-and-its-so-1823598400
the future speaks of 1000x speed of SSD with crosspoint :  https://www.geek.com/chips/new-intel-storage-is-1000-times-faster-than-your-ssd-1629656/

there"s also quantum ram coming :  https://www.itpro.co.uk/solid-state-storage-ssd/31387/what-the-future-holds-for-data-storage
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Commented:
SSDs aren't always faster than HDDs, sustained write on a QLC SSD may actually be slower than a fast HDD once the buffer is full. Once PLC SSDs hit the market their sustained write will be even slower. You wouldn't normally notice this since you're unlikely to fill the much faster cache that the SSD has except during a long OS install or software updates.

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Commented:
Thank you, everyone, for answering my question.

George