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Re: Measuring (or calculating) how many bytes are actually written to disk when I repeatedly save a file




On 2019-04-08, rhkramer@xxxxxxxxx <rhkramer@xxxxxxxxx> wrote:
>
> As mentioned in another post, I am starting to fear for the reilability of an 
> HDD (DOAs, early failures, unwilingness of the vendor / manufacturer to 
> provide a warranty), and, therefore, I am trying to determine if an SSD could 
> be a better choice.
>
> (Someday, I expect it will be -- is that day here?)
>
>

Here's one study for you (where number of writes and enterprise-grade
drives--mentioned by someone in this thread I believe--are found not to be
determining factors for longevity or reliability):

https://www.zdnet.com/article/ssd-reliability-in-the-real-world-googles-experience/

http://0b4af6cdc2f0c5998459-c0245c5c937c5dedcca3f1764ecc9b2f.r43.cf2.rackcdn.com/23105-fast16-papers-schroeder.pdf

 Two standout conclusions from the study. First, that MLC drives are as
 reliable as the more costly SLC "enteprise" drives. This mirrors hard drive
 experience, where consumer SATA drives have been found to be as reliable as
 expensive SAS and Fibre Channel drives.

 One of the major reasons that "enterprise" SSDs are more expensive is due to
 greater over-provisioning. SSDs are over-provisioned for two main reasons: to
 allow for ample bad block replacement caused by flash wearout; and, to ensure
 that garbage collection does not cause write slowdowns.

 The paper's second major conclusion, that age, not use, correlates with
 increasing error rates, means that over-provisioning for fear of flash wearout
 is not needed. None of the drives in the study came anywhere near their write
 limits, even the 3,000 writes specified for the MLC drives.

 But it isn't all good news. SSD UBER rates are higher than disk rates, which
 means that backing up SSDs is even more important than it is with disks. The
 SSD is less likely to fail during its normal life, but more likely to lose
 data.