[RabidSnail]

Solid State Drives are fast, but recently I have been seeing SSDs come to the market claiming to be faster that SATA connected SSDs. Specifically drives such as the Samsung Evo using mSATA connections. And I have also seen some SSDs that use PCIe. Is there really any speed difference between these connection differences?

 

[TrevJonez]

The pcie based solutions are the fastest. In my operating systems class my professor had showed us a video from one of his friends start-up venture. They were testing PCIe SSD's (recreating OEM quoted speed benchmarks) and showing that they are capable of moving so fast that with current software/system design you couldn't use the data at the rate they where capable of. Not even in an enterprise application. The ssd they had tested was able to deliver data so fast that the kernel in use (some form of linux) wasn't able to keep up with the SSD's delivery rate. And that was with the data simply being read and absolutely nothing being done to it.

I have that class in twenty minutes and will come edit this post with the info and video link as soon as i can.

EDIT:

here is the video http://vimeo.com/79543041

fairly long but interesting.

The company is called coho data.

 

[BradleyW]

This might help explain:
http://www.youtube.com/watch?v=0h7coK9Az84&list=UUNovoA9w0KnxyDP5bGrOYzg

 

[RabidSnail]

hmmm, interesting. I am by no means at a level where I can fully appreciate the video by TrevJonez, but I did watch both in an attempt to understand. So basically an SSD is faster than its transfer protocols, and currently nothing can handle the amount of data it transfers. The information bottlenecks somewhere.... But out of the three transfer interfaces, PCIe bottlenecks at the faster speed. And the video TrevJonez posted is a startup attempting to take this issue and more intelligently handle the bottleneck and increase overall efficiency. Is that the idea?

 

[TrevJonez]

yes exactly, So the real question comes to play. What are your wants and needs and what can be had for your budget. For the most part a good highend sata3 SSD is awesome for most. If you find yourself wanting more you can go to a RAID setup (arguably unnecessary by most) or to a PCI bus mounted solution such as the NGFF N.2 format or a more direct method such as a PCIe slot.

 

[CynicalUnicorn]

Quote:

Originally Posted by TrevJonez

yes exactly, So the real question comes to play. What are your wants and needs and what can be had for your budget. For the most part a good highend sata3 SSD is awesome for most. If you find yourself wanting more you can go to a RAID setup (arguably unnecessary by most) or to a PCI bus mounted solution such as the NGFF N.2 format or a more direct method such as a PCIe slot.

Pretty much. Even high-end drives aren't typically worth it. A solid mid-range drive is generally enough. RAID and PCIe solutions (which are generally just RAID 0 SSDs) have stupid amounts of bandwidth available, but if you don't know whether or not you need it, then you probably don't need it. Same goes for RAM drives.

M.2 is PCIe and/or mSATA, by the way. Some drives can use both depending on the slot, and others are PCIe exclusive with two or four lanes available.

Quote:

Originally Posted by RabidSnail

Samsung Evo using mSATA connections

Not true. 840 EVOs and Pros can utilize RAPID mode, a RAM cache, that smashes SATA III in benchmarks. In the real world, nothing actually changes. The drives themselves, however, are bottlenecked by the SATA interface, and mSATA is just the standard SATA we know and love on 2.5" and 3.5" drives minimized for small form-factor systems. The connections are otherwise the same.

 

[RabidSnail]

Thats another think I was thinking about a while ago, SSD RAIDs... should have included that in the topic.

Now Ill admit, I know I dont need the speed, I'm more curious on the current possibilities.

I built a $5k desktop last summer, and intentionally left one PCIe3 port open and the intent was to be able to upgrade from my 500GB Samsung 840 Pro to a PCIe based SSD when they became realistic (in price). Ill probably never make that jump, since the SSD that I have is a beast in itself. But its just nice to know where/ how the world of SSD is changing things.

So would it make sense to upgrade to four 128GB Samsung 840 Pro drives in RAID, or get a 500GB PCIe based SSD (if lets say I had the need for faster speeds)? And will this always be the case until there is a faster standard to transfer data through than PCIe3 and SATA3, or could new technologies such the video TrevJonez posted make one of those methods preferable in the future?

 

[CynicalUnicorn]

I'd take the PCIe drive for the convenience and having four fewer SATA ports used (and therefore open for upgrades), but it's really a toss-up. PCIe has 500MB/s (I think the only drives out and planned are rev 2, not rev 3) in both directions - a total of 1000MB/s of throughput - while SATA has 600MB/s combined. However, the fastest SSD controllers are only 1.5GB/s or so, and the RAID controller might bottleneck the SATA drives. There comes a point where interface just doesn't matter.

 

[TrevJonez]

http://www.newegg.com/Product/Product.aspx?Item=N82E16820226454&clickid=xsZWHVV0bygg2I01aFRKAV9YUkTTG73VWVQtVc0&iradid=97618&ircid=2106&irpid=79301&nm_mc=AFC-IR&cm_mmc=AFC-IR-_-na-_-na-_-na

based on that you are looking at about 1$ per gig and it is about the speed of a higher end sata drive. now if you really want to break the bank (>3$ per gig) and get really good speed from a single drive

http://www.newegg.com/Product/Product.aspx?Item=9SIA0AJ14N6007&clickid=xsZWHVV0bygg2I01aFRKAV9YUkTTG42NWVQtVc0&iradid=97618&ircid=2106&irpid=79301&nm_mc=AFC-IR&cm_mmc=AFC-IR-_-na-_-na-_-na

Myself i went the route of 4x the kingston 240gb drives in RAID 0. I bought mine over time and have had decent results. Makes it super fast for long sequential stuff but honestly i bet a single evo drive would beat me out on the random read since the RAID overhead wouldn't be in the way. I ended up costing about 600$ for all 4 drives and have the single large volume to work with which is what i wanted. The system as a result is VERY responsive in almost any and all work loads. MUCH better than the single 7200 rpm drive i had before. I have been very spoiled as of late.



Here is a fun little page, though it won't mean much to most look at all the labels and play with the slider up top. Really a cool demonstration of where we have improved over the years as far as memory comes to play.

http://www.eecs.berkeley.edu/~rcs/research/interactive_latency.html

So the chart was presented to me as a way to bring into perspective the amount of cpu cycles or time you lose when loading data. if you figure a common cpu is 3.6ghz these days and it takes you in the case of that chart. 2ms for a hard drive read. you would have waited for around 720 million cpu operations for the data to arrive. now granted the way modern operating systems and hardware work they do a good job of working on something else while those data seeks are happening. This all just gives weight to the idea of optimizing your code to fit in cache, ram, etc. The different settings of prime 95 come to mind since they vary the data set size to stress different parts of the system.

 

[CynicalUnicorn]

Quote:

Originally Posted by TrevJonez

http://www.newegg.com/Product/Product.aspx?Item=N82E16820226454&clickid=xsZWHVV0bygg2I01aFRKAV9YUkTTG73VWVQtVc0&iradid=97618&ircid=2106&irpid=79301&nm_mc=AFC-IR&cm_mmc=AFC-IR-_-na-_-na-_-na

based on that you are looking at about 1$ per gig and it is about the speed of a higher end sata drive. now if you really want to break the bank (>3$ per gig) and get really good speed from a single drive

http://www.newegg.com/Product/Product.aspx?Item=9SIA0AJ14N6007&clickid=xsZWHVV0bygg2I01aFRKAV9YUkTTG42NWVQtVc0&iradid=97618&ircid=2106&irpid=79301&nm_mc=AFC-IR&cm_mmc=AFC-IR-_-na-_-na-_-na

*snip*

Meh, that's a RAID card for 2x240GB M.2 drives. You'd be better off with three drives in RAID 0, or just two and an aftermarket RAID card - two lanes for RAID is a serious limitation given what controllers are capable of. OCZ? That's just overpriced, but it is a drive from 2011. There is not a huge market for PCIe drives as of now, unfortunately, but M.2 is slowly making its way into laptops. I think the new MacBooks are going to use them.

Yeah, latency is a big issue. Something like the L1 cache can be accessed in a few clock cycles. L2 might take a dozen or two. L3 can take up to 100 or so. RAM? 10 000. SSDs? Millions. HDDs? Might as well make yourself comfortable; we're gonna be here for a while. Sure, 5ms is imperceptible to a human, but think about how much efficiency, both in terms of time and energy, is wasted waiting on memory. I actually found THIS today while I was looking to see if there was any news about the ULLtraDIMM. There is a chart at the bottom of the page that puts latency into human terms. I think the magnetic tape can be disregarded.

 

[TrevJonez]

I totally agree, the cost of the pcie cards does not make sense unless you are constrained to the point where it is the only option.

That chart is awesome. 1 month for hard disk I/O. that would be the end of us all.

Since we have brought humans into the conversation, here is another pyramid worth a giggle.

 

[edplayer]

Quote:

Originally Posted by TrevJonez

They were testing PCIe SSD's (recreating OEM quoted speed benchmarks) and showing that they are capable of moving so fast that with current software/system design you couldn't use the data at the rate they where capable of. Not even in an enterprise application. The ssd they had tested was able to deliver data so fast that the kernel in use (some form of linux) wasn't able to keep up with the SSD's delivery rate. And that was with the data simply being read and absolutely nothing being done to it.

that doesn't make sense. System memory is substantially faster than what you can get from even a PCI-E based SSD and it definitely doesn't sit there unused. Just because you see one example doesn't mean that the millions of other possible examples won't work also...

 

[TrevJonez]

Quote:

Originally Posted by edplayer

that doesn't make sense. System memory is substantially faster than what you can get from even a PCI-E based SSD and it definitely doesn't sit there unused. Just because you see one example doesn't mean that the millions of other possible examples won't work also...

I am not trying to implicate every other possible hardware example just trying to show the progress of what this SSD stuff is. It was a limitation of the kernel implementation not the hardware. Obviously the hardware can do it given enough PCI lanes to work with.

Purely software limitation. The point being that a system that was designed really well had to be reworked a bit to keep up with evolving hardware speed. The speed upgrade of SSD is massive, my own mundane test from a single 7,200rpm drive to a 4xRaid-0 shows a 99.2% reduction in latency and a 1336% random reed speed upgrade. All for around 600$. That is the value of these SSD's and mine are cheap crap drives compared to the current market.

So one step further, If an enterprise server targeted kernel implementation couldn't use the data fast enough without modification. Can the consumer targeted solutions?