On 09/25/2012 09:38 PM, Jim Klimov wrote: > 2012-09-11 16:29, Edward Ned Harvey > (opensolarisisdeadlongliveopensolaris) wrote: >>> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss- >>> boun...@opensolaris.org] On Behalf Of Dan Swartzendruber >>> >>> My first thought was everything is >>> hitting in ARC, but that is clearly not the case, since it WAS >>> gradually filling up >>> the cache device. >> >> When things become colder in the ARC, they expire to the L2ARC (or >> simply expire, bypassing the L2ARC). So it's normal to start filling >> the L2ARC, even if you never hit anything in the L2ARC. > > > Got me wondering: how many reads of a block from spinning rust > suffice for it to ultimately get into L2ARC? Just one so it > gets into a recent-read list of the ARC and then expires into > L2ARC when ARC RAM is more needed for something else, and only > when that L2ARC fills up does the block expire from these caches > completely? > > Thanks, and sorry for a lame question ;)
Correct. See https://github.com/illumos/illumos-gate/blob/14d44f2248cc2a54490db7f7caa4da5968f90837/usr/src/uts/common/fs/zfs/arc.c#L3685 for an exact description of the ARC<->L2ARC interaction mechanism. Cheers, -- Saso _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
