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I have an Intel 320 SSD which is supposedly able to flush its cache during a power loss.

From Storage Review:

Rarely seen in a consumer SSD, Intel uses an array of capacitors to make sure data gets saved to the drive in the event of an unsafe shutdown as the result of power loss.

From Intel:

The Intel SSD 320 Series contains hardware- and firmware-based power-loss data protection features. The SSD includes a power-fail detection circuit, which sends a signal to the ASIC controller in the SSD indicating there is an imminent drop in power level. Triggered by this, SSD firmware disconnects the input power from the SSD.

The SSD then relies on its on-board power-loss protection capacitance to provide enough energy for the SSD firmware to move data from the transfer buffer and other temporary buffers to the NAND.

Does it mean I can safely turn off "Windows write-cache buffer flushing"? My primary motivation is to improve performance, although I'm aware that this might not make a big change for desktop workload.

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I don't think it will make any change at all –  soandos Jun 17 '12 at 5:08
    
Agreed I don't think it will make much of a difference. Write caching was added to deal with the slow write speeds of traditional hard drives which is much less of an issue with SSDs. –  Brad Patton Jun 20 '12 at 20:09

3 Answers 3

This doesnt make a lot of sense to me. Sure, they can have a capacitor in the drive to allow the SSD to flush its buffer to disk. But that doesnt mean the buffer had received all the data from the OS cache.

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As it turns out, intel is one of the few ssd brands which you will want to have flushing enabled. http://www.tomshardware.com/reviews/ssd-performance-tweak,2911-15.html

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Summary: turning off write flushing on the Intel X25-M G2 is detrimental to write performance. Nice to know. –  netvope Oct 16 '12 at 7:49

If you have to ask? Then it's not safe for you, and you should trust the defaults that your top-brand-name OS and SSD have been designed for.

I haven't read the documentation for this Windows option, but I know Linux has equivalent options. I would draw your attention to the ext4 filesystem and the "barrier" option, which is enabled by default. Barriers ensure the consistency of the FS on power-failure by enforcing ordering between certain writes. At least when it was first implemented, this involved forcing a flush of the write cache on the hard drive.

Only if the system as a whole is protected by a trusted UPS (i.e. a battery), and you trust the OS not to crash, then I believe it is safe to disable barriers on Linux. [I am not a professional. I am not your professional. Trust me at your peril]. I suspect the Windows option is designed for the same scenario. But IMO the second criteria pushes this into the realms of carefully administered servers.

That said, the exact level of risk depends on the filesystem. ext4 without barriers is much worse than ext3 (which didn't enable barriers by default). So if your version of Windows is more like ext3 in this respect, you could expect to find anecdotes of people running PCs with this option disabled for many years, and not noticing any problems.

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