7 ms·

Memory-Like Storage Means File Systems Must Change

52 points by Katydid 9y ago

cryptonector 9y ago
We were talking about this just days ago: https://news.ycombinator.com/item?id=14386626 https://news.ycombinator.com/item?id=14386626 (not that we're done, just merely providing a link for others)
- beagle3 9y ago
  Especially Howard Chu's (hyc_symas) comment, currently the top rated one.
cryptonector 9y ago
> “You have got this great big thickness of software that is between you and the hardware, and these new technologies, and 3D XPoint is the exemplary, forced me to see that everything has got to change,” explains [Eric] Barton. ... Absolutely. With long latencies you can do all sorts of complex things. The thing I really don't want to give up on is COW, but with COW writes get multiplied, so it may be an unaffordable luxury, even with write-ahead logging. One might log undo and redo logs and then write the rest lazily in-place -- that too gets some write magnification, but less so.
tutanchamun 9y ago
(ST-) MRAM sounds much beter than 3D Xpoint to a layman like me (speed and endurance like DRAM, so better than Xpoint), and seems to ship already from a small company, why is Xpoint the focus? Better marketing?
- cestith 9y ago
  The guy is leaving Intel, which was working on Xpoint during his employment there. Regardless of the relative merits, he likely had far more exposure as a file systems guy at Intel to storage technology being developed and sold by Intel.
- PeCaN 9y ago
  Because 2MB of MRAM for $43¹ is not exactly game-changing.² 3D-XPoint is more like a much faster SSD than real NVRAM. Everspin and other true NVRAM companies are trying very hard and making huge strides, but scaling density up to expected multi-gigabyte sizes is really hard. 3D-XPoint could be seen as a sort of stopgap for a few years or decades while NVRAM matures. That said, I think one of the NVRAMs—MRAM looks the most promising—will get there eventually, and it will change everything. I'm tinkering on a hobby OS to take advantage of single-level storage and cache-coherent interconnects like CCIX and GenZ. --- 1. https://www.digikey.com/products/en/integrated-circuits-ics/memory/774?k=&pkeyword=&pv142=1501&FV=fffc0333&mnonly=0&newproducts=0&ColumnSort=0&page=1&chp=0&quantity=0&ptm=0&fid=0&pageSize=25 https://www.digikey.com/products/en/integrated-circuits-ics/... 2. They announced 64MB modules a few months ago, but AFAICT those are yet to hit the market.
FrozenVoid 9y ago
3Dxpoint is essentially a faster flash with all the problems of NAND cells. Its not memory-like with limited write endurance. >While Intel claims the new non-volatile storage medium will offer significant improvements in endurance, performance, and power consumption (10x lower latency, 3x write endurance, 4x more writes per second, and as little as 30% the power consumption as competing NAND flash) https://www.extremetech.com/computing/237817-first-intel-optane-hardware-could-be-coming-to-consumer-desktops https://www.extremetech.com/computing/237817-first-intel-opt... >3D XPoint memory has better endurance than NAND flash, but not enough to get away without wear levelling http://www.anandtech.com/show/11209/intel-optane-ssd-dc-p4800x-review-a-deep-dive-into-3d-xpoint-enterprise-performance http://www.anandtech.com/show/11209/intel-optane-ssd-dc-p480...
- lodi 9y ago
  It's "memory-like" because it's byte-addressable. Flash forces you to read a whole page to read a single byte.
  - FrozenVoid 9y ago
    Normal RAM also forces you to read the page to L1/L2 cache. Is RAM not byte-addressable? See https://en.wikipedia.org/wiki/Cache_prefetching https://en.wikipedia.org/wiki/Cache_prefetching

52 points by Katydid 9y ago

We were talking about this just days ago: https://news.ycombinator.com/item?id=14386626 https://news.ycombinator.com/item?id=14386626 (not that we're done, just merely providing a link for others)

beagle3 9y ago
Especially Howard Chu's (hyc_symas) comment, currently the top rated one.

cryptonector 9y ago

> “You have got this great big thickness of software that is between you and the hardware, and these new technologies, and 3D XPoint is the exemplary, forced me to see that everything has got to change,” explains [Eric] Barton. ... Absolutely. With long latencies you can do all sorts of complex things. The thing I really don't want to give up on is COW, but with COW writes get multiplied, so it may be an unaffordable luxury, even with write-ahead logging. One might log undo and redo logs and then write the rest lazily in-place -- that too gets some write magnification, but less so.

tutanchamun 9y ago

(ST-) MRAM sounds much beter than 3D Xpoint to a layman like me (speed and endurance like DRAM, so better than Xpoint), and seems to ship already from a small company, why is Xpoint the focus? Better marketing?

cestith 9y ago
The guy is leaving Intel, which was working on Xpoint during his employment there. Regardless of the relative merits, he likely had far more exposure as a file systems guy at Intel to storage technology being developed and sold by Intel.
PeCaN 9y ago
Because 2MB of MRAM for $43¹ is not exactly game-changing.² 3D-XPoint is more like a much faster SSD than real NVRAM. Everspin and other true NVRAM companies are trying very hard and making huge strides, but scaling density up to expected multi-gigabyte sizes is really hard. 3D-XPoint could be seen as a sort of stopgap for a few years or decades while NVRAM matures. That said, I think one of the NVRAMs—MRAM looks the most promising—will get there eventually, and it will change everything. I'm tinkering on a hobby OS to take advantage of single-level storage and cache-coherent interconnects like CCIX and GenZ. --- 1. https://www.digikey.com/products/en/integrated-circuits-ics/memory/774?k=&pkeyword=&pv142=1501&FV=fffc0333&mnonly=0&newproducts=0&ColumnSort=0&page=1&chp=0&quantity=0&ptm=0&fid=0&pageSize=25 https://www.digikey.com/products/en/integrated-circuits-ics/... 2. They announced 64MB modules a few months ago, but AFAICT those are yet to hit the market.

FrozenVoid 9y ago

3Dxpoint is essentially a faster flash with all the problems of NAND cells. Its not memory-like with limited write endurance. >While Intel claims the new non-volatile storage medium will offer significant improvements in endurance, performance, and power consumption (10x lower latency, 3x write endurance, 4x more writes per second, and as little as 30% the power consumption as competing NAND flash) https://www.extremetech.com/computing/237817-first-intel-optane-hardware-could-be-coming-to-consumer-desktops https://www.extremetech.com/computing/237817-first-intel-opt... >3D XPoint memory has better endurance than NAND flash, but not enough to get away without wear levelling http://www.anandtech.com/show/11209/intel-optane-ssd-dc-p4800x-review-a-deep-dive-into-3d-xpoint-enterprise-performance http://www.anandtech.com/show/11209/intel-optane-ssd-dc-p480...

lodi 9y ago
It's "memory-like" because it's byte-addressable. Flash forces you to read a whole page to read a single byte.
- FrozenVoid 9y ago
  Normal RAM also forces you to read the page to L1/L2 cache. Is RAM not byte-addressable? See https://en.wikipedia.org/wiki/Cache_prefetching https://en.wikipedia.org/wiki/Cache_prefetching