Ever trying to gain just another percent of performance out of an admittedly sub-par setup, I have arrived at the sync parameter of zfs. Digging through some boards told me that disabling sync should be kinda-sorta ok if I trust my power supply, the data on the servers is well backed up and a lost day isn't the end of the world, performance is king here.
I noticed, though, that the sync for rpool/swap is set to "always" by default. Now, even though it shouldn't swap too much (swappinees is set to 1, the VMs use about 25% of the total physical ram), the system does swap for some odd reason every now and then and this seems to mean a performance hit.
Why is sync set to always (not just standard but actually always) by default on rpool/swap? What's the potential danger of disabling it?
I noticed, though, that the sync for rpool/swap is set to "always" by default. Now, even though it shouldn't swap too much (swappinees is set to 1, the VMs use about 25% of the total physical ram), the system does swap for some odd reason every now and then and this seems to mean a performance hit.
Why is sync set to always (not just standard but actually always) by default on rpool/swap? What's the potential danger of disabling it?