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Flash & Phase Change Memory Talks

This week, I attended talks at the international high performance transaction workshop. Following are my rough notes from the Flash Memory discussions.

First up Steve Kleiman from Network Appliance spoke about their intent to move  flash into the clients that access NAS, so that it can intelligently cache and interact with the backend storage:

• Netapp is building host-side caches for VMware and HyperV
• The cache will be a block based read cache 
• Cache is write through

Andy Bechtolshiem, cofounder of Sun and now at Arista Networks talked about trends affecting system design and how Flash could be leveraged.

• 3d chip packaging will become common, to solve power and latency fundamentals around higher clock rate memory systems. 
• This will mean that systems will become very NUMA, since the memory is directly attached to the cpu core.
• This is the decade where we switch to optical in the datacenter. Cutover is 10gbit (copper), 20 requires optical and will move to volume commodity optical interconnects for distances greater than 1m.
• Flash densities to grow 100x between 2010 and 2022
• Processors will have 1024 cores in 2022
• NOR flash is not scaling as well as NAND flash, in terms of cost and density
• Major barrier to non-voltaile main memory is the single host failure issue.
• Current controllers (flash on sata) are not up to the speed
• Speed of flash increases from 100us down to 10us from 2009 to 2012
• ASP per $1GB of device flash $100 in 2004 to $1/gb in 2010 and 0.25c in 2012 (Halves every year)
• Controllers improving rapily to keep up with flash throughput (they are deficient now)
• Flash Interface moving from sata to pci-e in the near term

Microsoft Research Database - Phil Bernstein, Microsoft

• DB designed specifically for flash
• no-partitioning
• Taking advantage of native-flash chip semantics :append-only, db using log-appends, Updates the flash in append-only pages
• Database is ZFS-like: root block, copy on write binary tree 
• Uses a shared storage layer
• MySql “rethinkdb?” is doing something similar

Bradley Kurszmaul, Tokutek

• MySQL on SSD btree performance severely lacking
• Solution: build a MySQL storage engine suited for flash
• Observation: change read/write sizes and concurrency to suite: for today’s flash: ~20k reads, ~10k writes.
• Significant improvement in transaction throughput observed using the above.

IBM on Phase Change Memory

• Next generation after flash: Phase Change Memory
• Prediction is that SCM/PCM will flip the size relationship between RAM and 2nd level memory
• Much more 2nd level, small fast on-chip RAM
• PCM as fast as 100-1000ns
• Discussion centered around Flash being a short term trend, and due to limitations (wear leveling etc) PCM is more likely to be part of the systems architecture long term.