On Wed, Nov 20, 2013 at 10:37:03AM -0500, Theodore Ts'o wrote: > On Wed, Nov 20, 2013 at 08:52:36PM +0530, Chinmay V S wrote: > > > > If you have confirmed the performance numbers, then it indicates that > > the Intel 530 controller is more advanced and makes better use of the > > internal disk-cache to achieve better performance (as compared to the > > Intel 520). Thus forcing CMD_FLUSH on each IOP (negating the benefits > > of the disk write-cache and not allowing any advanced disk controller > > optimisations) has a more pronouced effect of degrading the > > performance on Intel 530 SSDs. (Someone with some actual info on Intel > > SSDs kindly confirm this.) > > You might also want to do some power fail testing to make sure that > the SSD is actually flusing all of its internal Flash Translation > Layer (FTL) metadata to stable storage on every CMD_FLUSH command. Some SSD's are also claim the ability to flush the cache on power loss: http://www.intel.com/content/www/us/en/solid-state-drives/ssd-320-series-power-loss-data-protection-brief.html Which should in theory let them respond immediately to flush requests, right? Except they only seem to advertise it as a safety (rather than a performance) feature, so I probably misunderstand something. And the 520 doesn't claim this feature (look for "enhanced power loss protection" at http://ark.intel.com/products/66248), so that wouldn't explain these results anyway. --b. > > There are lots of flash media that don't do this, with the result that > I get lots of users whining at me when their file system stored on an > SD card has massive corruption after a power fail event. > > Historically, Intel has been really good about avoiding this, but > since they've moved to using 3rd party flash controllers, I now advise > everyone who plans to use any flash storage, regardless of the > manufacturer, to do their own explicit power fail testing (hitting the > reset button is not good enough, you need to kick the power plug out > of the wall, or better yet, use a network controlled power switch you > so you can repeat the power fail test dozens or hundreds of times for > your qualification run) before being using flash storage in a mission > critical situation where you care about data integrity after a power > fail event. > > IOW, make sure that the SSD isn't faster because it's playing fast and > loose with the FTL metadata.... > > Cheers, > > - Ted > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
