Hi, I discovered the cause of my problem - Intel Rapid Start Technology (IRST).
Basically there is a hidden hibernation partition (different to hiberfil.sys) used by IRST.
The IRST is set to activate by default (on my system) after 120 minutes.
So after 2 hours of sleeping, drive activity would commence and the active user session in RAM would be written to the Hibernation Partition (8GB in my case).
The problem came during resume, when pressing the power button, it failed to restore the session from the SSD to the RAM, and I got a failed boot.
A second press cold booted the system to a fresh desktop with any unsaved work lost.
A workaround in my case was to disable IRST either in the bios or in the systray utility.
Ultimately the solution was a new motherboard, which was put in by Dell yesterday.
Sleep / IRST & Hibernate all work fine now.
Interestingly hiberfil.sys (6.6GB) is ONLY used for booting in this setup:
Sleep - RAM
Extended Sleep (IRST) - hibernation partition
Re-boot - is now (under windows 8 with 'fast startup' enabled) effectively a 'cold boot' ie read from disk
Shut down / PowerOn - is now effectively a 'warm boot' as it reads from hiberfil.sys
So there is some disk redundancy with the 2 systems (IRST and 'Windows Hibernate'), you could effectively utililize just one system with little difference in performance.
To be honest I am hard pressed to measure any difference in speed between any of the following:
- a hiberfil.sys assisted boot
- a IRST 'resume'
- a Windows Hibernate resume
All of these are getting my system to a login prompt in about 6 secs from power button press.
At the moment I have all of them enabled, but may change to reclaim disk space.
Not sure most of that was relevant to you!
G :)
Couple of other points:
S0 = on
S1, S2, S3 are various forms of sleep, depending on manufacturer, generally RAM is powered all else is off.
S4 is hibernate or IRST
S5 is off / shut down