On Jun 25, 2008, at 11:49 AM, Darren Reed wrote: > This would seem to be a significant use case for the model of having > non-overlapping data types in each of the two caches. Since no reply > was received on zfs-discuss, I'm redirecting it to psarc to indicate > that > this question isn't closed.
I see some comments, but no direct question. So what is the question? eric > > > Darren J Moffat wrote: >> Darren Reed wrote: >> >>> So I spent some time thinking about different directions you could >>> build >>> on this in the future, for example: >>> 1) controlling the size of the ARC/L2ARC by controlling the cache >>> size >>> 2) specifying different backing storage for primary/secondary cache >>> 3) having more than two levels of cache >>> ...none of which is precluded by current efforts. >>> >>> With (2), if the backing storage for each cache is different and >>> it is slower >>> to access the secondary cache than the primary, then you may not >>> want >>> metadata to be stored in the secondary cache for performance >>> reasons. >>> >>> As an example, you might be using NVRAM (be it flash or otherwise) >>> for the primary cache and ordinary RAM for the secondary. In this >>> case >>> you probably don't want any metadata to be stored in the secondary >>> cache (power failure issues) but the same may not hold for user >>> data. >>> But I'm probably wrong about that. >>> >> >> I doubt you would be, the primarycache is system memory not a cache >> device. The secondarycache is the L2ARC devices specified with the >> "cache" vdev type to zpool so your examle would be the otherway >> around. >> >>
