jgreco
Resident Grinch
- Joined
- May 29, 2011
- Messages
- 18,681
Wow. That doesn't help much with the need for lots of ARC in the first place to correctly identify interesting blocks (still thinking about this in terms of VM datastore), but it does potentially change the game for the amount of L2ARC you could attach to such a system.
The thing is that memory prices haven't fallen as rapidly as SSD prices, so it is very attractive to have the possibility to maybe triple(?) the L2ARC:ARC ratio. The VM filer here has 64GB RAM and a 256GB L2ARC, and that's pretty fine. If I can triple the L2ARC, that's pretty sweet, but there's also an argument that the RAM could be boosted to 128GB, and more of the ARC could be set aside for metadata, and I could punch L2ARC up past a terabyte which would cover our working set very thoroughly, for relatively modest cost (compared to going to 256GB RAM and 1TB+ L2ARC). The current cost for 128GB RAM is still around $1200...
The thing is that memory prices haven't fallen as rapidly as SSD prices, so it is very attractive to have the possibility to maybe triple(?) the L2ARC:ARC ratio. The VM filer here has 64GB RAM and a 256GB L2ARC, and that's pretty fine. If I can triple the L2ARC, that's pretty sweet, but there's also an argument that the RAM could be boosted to 128GB, and more of the ARC could be set aside for metadata, and I could punch L2ARC up past a terabyte which would cover our working set very thoroughly, for relatively modest cost (compared to going to 256GB RAM and 1TB+ L2ARC). The current cost for 128GB RAM is still around $1200...