flash - To what extent is size a factor in SSD performance?
2013-08
artif
To what extent is the size of an SSD a factor in its performance?
In my mind, correct me if I'm wrong, a bigger SSD should be, everything else being equal, faster than a smaller one. A bigger SSD would have more erase blocks and thus more leeway for the FTL (flash translation layer) to do garbage collection optimization. Also there would be more time before TRIM became necessary. I see on Wikipedia that it remarks that "The performance of the SSD can scale with the number of parallel NAND flash chips used in the device" so it seems throughput also increases significantly. Also many SSDs contain internal caches of some sort and presumably those caches are larger for correspondingly large SSDs.
But supposing this effect exists, I would like a quantitative analysis. Does throughput increase linearly? How much is garbage collection impacted, if at all? Does latency stay the same? And so on. Would the performance of a 8 GB SSD be significantly different from, for example, an 80 GB SSD assuming both used high quality chips, controllers, etc?
Are there any resources (webpages, research papers, presentations, books, etc) that discuss correlations between SSD performance (4 KB random write speed, latency, maximum sequential throughput, etc) and size? I realize this does not really sound like a programming question but it is relevant for what I'm working on (using flash for caching hard drive data) which does involve programming.
If there is a better place to ask this question, eg a more hardware oriented site, what would that be? Something like the equivalent of stack overflow (or perhaps a forum) for in-depth questions on hardware interfaces, internals, etc would be appreciated.
artif
Thanks James. It doesn't fully answer my question but there are some useful tidbits. To summarize some of the relevant parts of those talks:
SSD performance can increase by 10% or more as the "spare area" on the SSD increases.
Increases in spare area on MLC (vs SLC) is particularly good at increasing performance.
Most of the SSDs which are reasonably big tend to use MLC, which has somewhat higher latency and lower write bandwidth, but comparable read bandwidth.
So drawing from this, it seems that a bigger SSD will probably have higher performance than a smaller SSD, unless the reason the smaller SSD is smaller is because it uses SLC or it has a higher percentage of spare.
This is mostly what I expected but it's nice to see confirmation.
Another useful but again not entirely comprehensive look comes from just scanning some of the tech specs on the web. For example I look a look at OCZ's page here on the Vertex Turbo. It seems that throughput does not come at all close to linearly increasing with drive size. It takes a jump from 30 GB to 120 GB to see a significant difference, and even then mainly for write speed not read.
sblair
Check out MEMS002 and MEMS003 from Intel's Developer Forum found here: https://intel.wingateweb.com/us09/scheduler/catalog/catalog.jsp
Brad Patton
Storage Review has an excellent review of 6 Corsair Force Series GT drives in different sizes (from 60GB to 480GB). The summary is that larger drives in the family perform better in most scenarios (but not all). 240 GB seems to be the sweet spot (at least for the SandForce controller).
XHR
I'm going to be building a new system soon and I'm willing to spend a few more dollars to improve my hard drive performance. This will be a general use system so I just want to see HD intensive tasks in general go faster whether it be booting, application loads, game loads, maybe video editing, whatever.
My initial thought was to just buy 2 WD Raptors, RAID-0 them together and then just get a regular 1TB+ 7200 SATA drive for storage. The raptors would be my OS drive and all my installs would go there. I could perform whatever work I feel like on the OS drive and then when done move it over to the storage drive. Thus, its not too big a deal if one of the raptors failed, I would just have to reinstall everything.
Thing is, in reading some reviews, not everyone is impressed or notices speed improvements. This gets me to look at other options and honestly there are so many that it seems almost impossible to know what the best is for a medium price range.
SSD's have crazy differences in speeds between manufacturers and models, in the hundreds of Mbps! They also scare me right now, various reports of weird behavior like application freezes and such. I think I've actually experienced this on my SSD Eee netbook, though I can't confirm its the SSD's fault. Maybe the more expensive models don't have this issue. SAS 15k drives are comparable to the raptor's in cost and have better performance but it looks like a decent controller card will run you 200-300 easy.
Honestly right now I'm considering just getting a couple 1-1.5TB standard 7200 drives and raid-0 them together. It would be a huge waste of space as I have no use for that much room for an OS drive but it actually seems like a decent idea as I can probably do that for under $200 and still get a performance boost. Would it be slower than a single raptor (price is about the same at this point), hard to know really unless someone does a side by side comparison. People have done reviews I know but they get outdated fast as speeds and cache sizes improve on a regular basis.
I guess a 100% certain answer to the best combination for your money is pretty much impossible as nearly every combination out there amongst various models and types would need to be evaluated. So I guess I really would just like to get some insight into what generally will be a performance boosting setup for a mid range price (200-500). Thanks.
user10762
I have never found raid arrays really make that much of a positive performance boost for every day use. They certainly don't improve access times and that is what you tend to notice most in general use. I would also avoid raid-0 unless you don't care about the data being stored.
An SSD is the way to go to get a noticeable speed boost. Use a modest sized (60-128GB) one for a boot drive and a larger mechanical drive for bulk storage. If you want your games to load faster they should be kept on the SSD in which case you might want to get a larger drive (120GB+).
Almost any fairly recent SSD should be OK but Intel is best followed by drives based on Samsung or Indilinx controllers (Samsung are probably safer and Indilinx slightly faster). Cheaper drives based on JMicron controllers are OK only if you are on a very tight budget. If the price is cheap and there is no mention of the controller then assume it is JMicron based regardless of how impressive the specs might seem.
John T
The Intel X-25M fits well into your budget and has had great reviews. Even Linus Torvalds has been impressed with his Intel SSD. The X-25E performs better but only provides 32GB space, at a fairly higher price. If you choose a SSD, I'd only keep the OS on it and programs you use frequently that require high data transfer speeds. Other programs can be installed to a seperate 7200rpm disk.
check out tomshardware hard drive benchmarks. they benchmark all kinds of different drives from 3.5" to SSDs. There is also price included beside each one.