Re: Measuring (or calculating) how many bytes are actually written to disk when I repeatedly save a file
- Date: Mon, 8 Apr 2019 16:52:42 -0000 (UTC)
- From: Curt <curty@xxxxxxx>
- Subject: 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):
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