> > > > I'm unclear on the best way to warm data... do you mean to simply `dd > if=/volumes/myvol/data of=/dev/null`? I have always been under the > impression that ARC/L2ARC has rate limiting how much data can be added to > the cache per interval (i can't remember the interval). Is this not the > case? If there is some rate limiting in place, dd-ing the data like my > example above would not necessarily cache all of the data... it might take > several iterations to populate the cache, correct? >
Quick update... I found at least one reference to the rate limiting I was referring to. It was Richard from ~2.5 years ago :) http://marc.info/?l=zfs-discuss&m=127060523611023&w=2 I assume the source code reference is still valid, in which case a population of 8MB per 1 second into L2ARC is extremely slow in my books and very conservative... It would take a very long time to warm the hundreds of gigs of VMs we have into cache. Perhaps the L2ARC_WRITE_BOOST tunable might be a good place to aggressively warm a cache, but my preference is to not touch the tunables if I have a choice. I'd rather the system default be updated to reflect modern hardware, that way everyone benefits and I'm not running some custom build.
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