Jorgen,
based on personal experience I'd be careful to claim that SSDs are more reliable than HDs. While a total failure is indeed quite rare, performance variation with many brands is much higher than with HDs.
Bjorns comment on SSD performance degradation with relatively low usage and being very slow is an indication that the mentioned SSD is using a threshold based GC (Garbage collection) approach vs. realtime GC/WL. If the SSD controller is fast enough to do realtime GC faster than the max write rate of the SSD, write performance variation diminishes almost completely over the lifetime of the SSD.
The combination of realtime GC and faster GC than the max write rate for a particular SSD type is a necessary precondition if SSDs should be combined in larger raid configurations with predictable (write) performance. Most consumer SSDs failed in this regard when I did my analysis a while ago.
I built quite a few of those open systems for very high sustainable combined I/O and compute performance (my second hobby besides photography).
Due to cost reasons I had to use consumer SSDs. Given the high number of SSDs needed (approx 100), I spent more than 2 months to evaluate 15 different consumer brands, before choosing the right model for my use case.
Here is a picture of one of these machines. 4 sockets, 32 physical cores, 512 GB RAM, 96 SSDs
This particular configuration had applications running with very high computational intensity (measured via energy consumption) and high sustainable I/O (
average write rate > 10 GB/s for a full week per run). Over the course of the year, each of the SSDs experienced a significantly higher write volume than guaranteed by the manufacturer. The drives didn't fail completely, but at the end write performance in about 10% of the total number of drives went down. (Was ok for me, as they served much longer than anticipated. Some drives had 20x the max. write volume the manufacturer listed). The other consumer drives I evaluated had much more erratic write behaviour under sustainable load.
BTW, loading a 100 GB data file from the SSDs into main memory took less than 5 seconds - a very convenient speed to work with....
Getting back on the HD failures rates and causes.
For those interested: Google published such a
statistical report (they have quite a few drives)
rgds,
Andy