On 05/04/2011 03:24 PM, David Boreham wrote:
So if someone says that SSDs have "failed", I'll assume that they
suffered from Flash cell
wear-out unless there is compelling proof to the contrary.
I've been involved in four recovery situations similar to the one
described in that coding horror article, and zero of them were flash
wear-out issues. The telling sign is that the device should fail to
read-only mode if it wears out. That's not what I've seen happen
though; what reports from the field are saying is that sudden, complete
failures are the more likely event.
The environment inside a PC of any sort, desktop or particularly
portable, is not a predictable environment. Just because the drives
should be less prone to heat and vibration issues doesn't mean
individual components can't slide out of spec because of them. And hard
drive manufacturers have a giant head start at working out reliability
bugs in that area. You can't design that sort of issue out of a new
product in advance; all you can do is analyze returns from the field,
see what you screwed up, and do another design rev to address it.
The idea that these new devices, which are extremely complicated and
based on hardware that hasn't been manufactured in volume before, should
be expected to have high reliability is an odd claim. I assume that any
new electronics gadget has an extremely high failure rate during its
first few years of volume production, particularly from a new
manufacturer of that product.
Intel claims their Annual Failure Rate (AFR) on their SSDs in IT
deployments (not OEM ones) is 0.6%. Typical measured AFR rates for
mechanical drives is around 2% during their first year, spiking to 5%
afterwards. I suspect that Intel's numbers are actually much better
than the other manufacturers here, so a SSD from anyone else can easily
be less reliable than a regular hard drive still.
--
Greg Smith 2ndQuadrant US greg@xxxxxxxxxxxxxxx Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books
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