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Bringing SSD Performance to the DIMM form factor

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Re: Bringing SSD Performance to the DIMM form factor

#171

Post by kalleboo »

tfb wrote: post #43
saticmotion wrote: post #15

Earlier quoted context omitted.

If it behaves like RAM, from the POV of the OS, I'd imagine the advantage to be the large size. There's also the fact that it won't lose its data on power loss. Of course, if it behaves like a regular SSD, the read speeds still exceed SATA3.0 speed.

> There's also the fact that it won't lose its data on power loss. Does this mean that for software to take full advantage of this, the software will need to be updated to account for it? For instance, Redis loads data into memory from disk upon starting, but if something like this 400GB SSD is available as memory (and say for instance, 300GB is in use by Redis), wouldn't it make sense for Redis, upon starting, to ju…

In the hypothetical world where this was as fast as real RAM, it would be cool if the OS was smart enough to read mmap'd data onto it and deal with remembering "this file was mmap'd here and hasn't changed since, next time it's mmap'd again we can just reuse it", and instantly you have support for all the software that just uses mmap (comedy MongoDB option?)

Re: Bringing SSD Performance to the DIMM form factor

#172

Post by sargun »

13 wrote: post #158
rsync wrote: post #155

Earlier quoted context omitted.

Aren't there plenty of other PCIe ram-cards ? Like http://ddrdrive.com/ ? I didn't think there was any shortage of these kind of devices - especially given their common use in ZFS workloads as a SLOG.

I couldn't find any when I looked recently, even the one you've linked to is quite old (2009) and has the same 4GB (presumably 32bit) limit. If they were more common and in more realistic sizes I'd love to get my hands on one.

How interested are you, and in what quantity, and what storage quantity do you want to buy them?

Re: Bringing SSD Performance to the DIMM form factor

#173

Post by solarmist »

jacquesm wrote: post #138
justincormack wrote: post #62

Earlier quoted context omitted.

I am not sure it is even a real project. I tried to find anyone working on it and failed. Nice story though.

It's very much real but I'm not sure if I agree with the basic premise. 'Regular' operating systems have gone through a whole slew of storage changes relatively unscathed, what it is about faster persistent storage that you could not encapsulate the same way we did with memory mapped files I do not understand. Obviously HP is far from stupid (or at least, its scientists are) but for now I'm on the fence if this is go…

You're right this isn't really a revolution in computing, but a unification. The hardware will be revolutionary, but the changes at the OS level will probably not be.

Still they're merging entire sub-systems that have existed independently for decades and someone has to actually make all the changes to support permanent in-place execution of code and the like that's what I mostly got out of the OS porting news.

Re: Bringing SSD Performance to the DIMM form factor

#174

Post by sixdimensional »

egillie wrote: post #146

SSDs as RAM + projects like Tachyon are the future of big data processing -- current workflows are still way too slow. I wonder how this will affect Spark.

I am not a silver bullet kind of person, but I think this kind of technology plus things like Spark are potentially the holy grail. Ok, let me rephrase - I've often believed that there was a sort of "ultimate architecture" with distributed cluster computing, distributed programming frameworks, high-speed interconnect, and flash based storage. I think we are getting closer and closer each day. I wish I worked in R&D at any of the companies doing this fundamental research now - I have a feeling they have some amazing things cooked up behind closed doors.

Re: Bringing SSD Performance to the DIMM form factor

#175

Post by vidarh »

com2kid wrote: post #143
vidarh wrote: post #103

Earlier quoted context omitted.

It's still way too slow to be treated as RAM. The performance they quote is equivalent to a mid to lower range PCIe SSD. For comparison, the stated read performance is 800MB/sec or so. Last time I checked - on ca. 8 year old hardware, we could read files from a RAM disk under Linux at a rate of about 6GB/sec. That's with the added overhead of the benchmark software running and going through a filesystem.

I wouldn't say that 800MB/s is slow. http://en.wikipedia.org/wiki/PC133 I also wonder if that 880 is for just one slot filled up. If it is, then I wonder if you can parallelize to 4 slots for ~3.4GB/s. At that point, I imagine many types of data sets would work A-OK. Though I wonder how that's scaled for cores, given that in the situation I imagined above, you'd be streaming all that data to just one CPU to get that…

Yes, it is slow. PC133 is "ancient". As I pointed out, even in 8 year old hardware it was trivial to get more than 6 times that performance out of a RAM disk device using filesystem benchmarking tools.

> If it is, then I wonder if you can parallelize to 4 slots for ~3.4GB/s

You probably can, but then you can't run code straight out of it, or read/write data directly as if it is normal RAM. Putting a filesystem on it, RAID'ed over multiple slots will likely work great (especially so since it's easy to get servers with a ton of DIMM slots, and it'll allow much better server density than trying to fit in more drive slots). But treating it as RAM will be slow.

Re: Bringing SSD Performance to the DIMM form factor

#176

Post by justincormack »

dgacmu wrote: post #127
justincormack wrote: post #62

Earlier quoted context omitted.

I am not sure it is even a real project. I tried to find anyone working on it and failed. Nice story though.

I know several researchers there who're working on it. It's for real. It's risky and ambitious, but it's a real, serious project (with tons of sub-research-projects, as you might imagine for something that requires multiple hardware advances and software advances to achieve.) (source: I'm a cs professor at carnegie mellon, and I was just chatting with some of those researchers at OSDI.)

Cool. I wanted to find someone to talk at https://operatingsystems.io/ about the OS bits (obviously there are lots of bits to it) - its a bit late now for 2 weeks time but if you know anyone appropriate put then in touch for next time... email in profile.

Re: Bringing SSD Performance to the DIMM form factor

#177

Post by justincormack »

mfisher87 wrote: post #128
justincormack wrote: post #62

Earlier quoted context omitted.

I am not sure it is even a real project. I tried to find anyone working on it and failed. Nice story though.

I know someone at HP who recently got a job on this project. So... it's not a lie?

Cool, put them in touch (see post above).

Re: Bringing SSD Performance to the DIMM form factor

#178

Post by justincormack »

mfisher87 wrote: post #128
justincormack wrote: post #62

Earlier quoted context omitted.

I am not sure it is even a real project. I tried to find anyone working on it and failed. Nice story though.

I know someone at HP who recently got a job on this project. So... it's not a lie?

Cool, put them in touch (see post above).

Re: Bringing SSD Performance to the DIMM form factor

#179

Post by 13 »

sargun wrote: post #172
13 wrote: post #158

Earlier quoted context omitted.

I couldn't find any when I looked recently, even the one you've linked to is quite old (2009) and has the same 4GB (presumably 32bit) limit. If they were more common and in more realistic sizes I'd love to get my hands on one.

How interested are you, and in what quantity, and what storage quantity do you want to buy them?

Not that interested, I'm an individual not a company! I meant if they were a product you could get off the shelf I'd be buying one, but I'm not that rich.
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