Isn't NVRAM slower than system RAM? So in theory could cause a bottleneck (this may no longer be true but you don't also have to wait for a CP on system RAM). Also, because the data is buffered this way should generally be a sequential write (assuming IO size)

On 01/20/2014 05:33 PM, Jeff Mohler wrote:

PS: I think we just agreed. :)

But its good to make the hard point, that NVRAM is not part of a write. Its common to see it as such, but it's systemically more correct to never mention NVRAM when talking about writes..cuz it doesnt matter. Its just a protection.

On Mon, Jan 20, 2014 at 2:31 PM, Jeff Mohler <speedtoys.racing@gmail.com> wrote:

No..NVRAM is not in the actual path of a write IO to disk.

Writes go to system RAM, a copy is made to NVRAM, when the system RAM space allocated is 1/2 full or the timer goes off..then writes are made to disk and the NVRAM copy is discarded.

NVRAM is there, but not part of the IO path to disk, it is beside it, and un-used unless the system crashed before RAM blocks were fully committed to disk.

On Mon, Jan 20, 2014 at 2:26 PM, Michael Bergman <michael.bergman@ericsson.com> wrote:

Couldn't resist... (sorry)

Jeff Mohler wrote:

:s/NVRAM/System Memory/g

Fixed it for ya.

Shouldn't that be more like

:s/NVRAM/System Memory plus a copy into NVRAM including mirror across to the HA cluster partners (if any) NVRAM, before returning with 'written OK'/g

:-)

/M

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