SSD "Enable Write Caching" turning back on after being turned off

Windows 7 Ultimate x64 SP1. I've noticed this strange behaviour where, after I have un-ticked "Enable write caching" for the main (only) drive in my laptop (Intel 240GB SSD) the setting keeps getting turned on again every time Windows wakes up from sleep. I turn if off again, and then it's on again after waking up.



What could be causing this, and is there another way (eg. group policy or registry setting) of forceably, permanently, disabling write caching? Or could this be some sort of driver issue? I wouldn't have thought turning a feature *off* would be a problem though. :)

ThrashZone said:

Hi and welcome to SevenForums,
Is hibernation disabled ?
Not a great thing to do on a laptop seeing it has a battery.

Hi ThrashZone, thanks. Hibernation is disabled, yes. How does that affect write caching? What isn't a great thing to do? Do you mean turning off write caching isn't good? I understand SSD life is mostly defined by writing, but I thought the danger of data corruption from power loss would be more important - ie. an SSD costs $100 but getting data back is far more costly in time. What is the prevailing wisdom about that?

Could Windows be turning it on again because that is just what it decides is right for SSDs?

Nobody knows how to keep write caching turned off? :)

bowtiebill said:

What isn't a great thing to do? Do you mean turning off write caching isn't good?

It's not a good idea to turn off write caching, mainly for the performance improvement it brings, but also because there aren't significant drawbacks to it either. It's a proven technique, with more than 20 years of use in a wide variety of systems. One has to have a very strong reason to disable it.
Why do you want to go without it?

bowtiebill said:

I understand SSD life is mostly defined by writing, but I thought the danger of data corruption from power loss would be more important - ie. an SSD costs $100 but getting data back is far more costly in time. What is the prevailing wisdom about that?

Both things are true I think, the data is far more important than the hardware. But your assumption is wrong, power loss will NOT corrupt data in the disk at all. Problem from power losses come from the fact that the OS may be stopped half-writing some data, and that for sure won't save it properly. Write caching exacerbates this problem by keeping data in RAM for longer before writing it to disk, so the window for data loss is somewhat greater. And also, are you getting constant power failures to worry about this?
Of course, that kind of data loss is always limited to the data the computer was writing at that very moments, or a few seconds ago at most. The rest is unaffected. Specially with modern filesystems like NTFS, they are reasonable resilient to failures even in system areas.

Besides, don't forget about backups. With a good backup set you can almost forget about all this. Even if your disk explodes right now, you just buy a new one (sorry wallet), restore the backup and continue as if nothing happened.

In short, don't try to disable it. You lose a significant performance improvement for pretty much nothing in return.

But to concretely answer the question, I really have no idea why that's happening
Even if it's a blunder, Windows MUST obey the user no matter what, and go and disable it if instructed to do so. My guess is that something else is enabling it back, maybe a driver or its support programs, or some kind of "optimizer" perhaps. But I don't have a concrete answer.

Thanks guys, ok I feel better about it now. :)

I only thought to turn caching off for the very reason that SSDs are much faster than HDDs, and traditionally write caching for HDDs was done purely for a speed increase. In that light, it seemed that if a non-cached SSD was just as fast (or faster) than a cached HDD, why not turn it off for the bit of extra data safety it brings? So I thought I'd try it, just to see how it goes, and found this issue.

However your points about flushing etc. are well made. I have had the odd problem over the years with a power outage and losing a file after the CHKDSK finishes, but it's very rare of course. Backups are a daily thing at best, so the possible loss of a few hours' work still niggles in the mind sometimes. Best thing I suppose is "autosave" in whatever software is being used, if it has it.

Speaking of backups, it's amazing how "tech savvy" kids seem to be, accumulating hundreds of gigs of photos, music, etc. yet hardly any of them know how to back stuff up! They seem to rely mainly on the "sync" services of MS, Apple and Google. Or Dropbox if they really "know how to use a computer". :) A friend's teenage daughter just spilled coffee on her Macbook, which was completely full of travel photos and stuff.. first thing I said was, "have you been backing it up?".. nope.