The SSD Anthology: Understanding SSDs and New Drives from OCZ
by Anand Lal Shimpi on March 18, 2009 12:00 AM EST- Posted in
- Storage
Bringing You Up to Speed: The History Lesson
Everyone remembers their first bike right? Mine was red. It had training wheels. I never really learned how to ride it, not that I didn’t go outdoors, I was just too afraid to take those training wheels off I guess. That was a long time ago, but I remember my first bike.
I also remember my first SSD. It was a 1.8” PATA drive made by Samsung for the MacBook Air. It was lent to me by a vendor so I could compare its performance to the stock 1.8” mechanical HDD in the Air.
The benchmarks for that drive didn’t really impress. Most application tests got a little slower and transfer speeds weren’t really any better. Application launch times and battery life both improved, the former by a significant amount. But the drive was expensive; $1000 from Apple and that’s if you bought it with the MacBook Air. Buying it from a vendor would set you back even more. It benchmarked faster than hard drive, but the numbers didn’t justify the cost. I pulled the drive out and sent it back after I was done with the review.
The next time I turned on my MacBook Air I thought it was broken. It took an eternity to boot and everything took forever to launch. Even though the benchmarks showed the SSD shaving off a few seconds of application launch time here and there, in the real world, it was noticeable. The rule of thumb is that it takes about a 10% difference in performance for a user to notice. The application tests didn’t show a 10% difference in performance, but the application launch tests, those were showing 50% gains. It still wasn’t worth $1000, but it was worth a lot more than I originally thought.
It was the MacBook Air experience that made me understand one important point about SSDs: you don’t think they’re fast, until I take one away from you.
My second SSD was a 60GB SuperTalent drive. I built a HTPC using it. It was my boot drive and I chose it because it drew less power and was silent; it helped keep my HTPC cool and I wouldn’t have to worry about drive crunching while watching a movie. My movies were stored elsewhere so the space didn’t really matter. The experience was good, not great because I wasn’t really hitting the drive for data, but it was problem-free.
SuperTalent was the first manufacturer to sell a SSD in a 3.5” enclosure, so when they announced their 120GB drive I told them I’d like to do a review of their SSD in a desktop. They shipped it to me and I wrongly assumed that it was the same as the 60GB drive in my HTPC just with twice the flash.
This drive did have twice the flash, but it was MLC (Multi-Level Cell) flash. While the 60GB drive I had was a SLC drive that used Samsung’s controller, the MLC drive used a little known controller from a company called JMicron. Samsung had a MLC controller at the time but it was too expensive than what SuperTalent was shooting for. This drive was supposed to be affordable, and JMicron delivered an affordable controller.
After running a few tests, the drive went in my Mac Pro as my boot/application drive. I remembered the lesson I learned from my first SSD. I wasn’t going to be able to fairly evaluate this drive until I really used it, then took it away. Little did I know what I was getting myself into.
The first thing I noticed about the drive was how fast everything launched. This experience was actually the source of my SSD proof-of-value test; take a freshly booted machine and without waiting for drive accesses to stop, launch every single application you want to have up and running at the same time. Do this on any system with a HDD and you’ll be impatiently waiting. I did it on the SuperTalent SSD and, wow, everything just popped up. It was like my system wasn’t even doing anything. Not even breaking a sweat.
I got so excited that I remember hopping on AIM to tell someone about how fast the SSD was. I had other apps running in the background and when I went to send that first IM and my machine paused. It was just for a fraction of a second, before the message I'd typed appeared in my conversation window. My system just paused.
Maybe it was a fluke.
I kept using the drive, and it kept happening. The pause wasn’t just in my IM client, it would happen in other applications or even when switching between apps. Maybe there was a strange OS X incompatibility with this SSD? That’d be unfortunate, but also rather unbelievable. So I did some digging.
Others had complained about this problem. SuperTalent wasn’t the only one to ship an affordable drive based on this controller; other manufacturers did as well. G.Skill, OCZ, Patriot and SiliconPower all had drives shipping with the same controller, and every other drive I tested exhibited the same problem.
I was in the midst of figuring out what was happening with these drives when Intel contacted me about reviewing the X25-M, its first SSD. Up to this point Intel had casually mentioned that their SSD was going to be different than the competition and prior to my JMicron experience I didn’t really believe them. After all, how hard could it be? Drive controller logic is nowhere near as complicated as building a Nehalem, surely someone other than Intel could do a good-enough job.
After my SuperTalent/JMicron experience, I realized that there was room for improvement.
Drive vendors were mum on the issue of pausing or stuttering with their drives. Lots of finger pointing resulted. It was surely Microsoft’s fault, or maybe Intel’s. But none of the Samsung based drives had these problems.
Then the issue was cache. The JMicron controller used in these drives didn’t support any external DRAM. Intel and Samsung’s controllers did. It was cache that caused the problems, they said. But Intel’s drive doesn’t use the external DRAM for user data.
Fingers were pointed everywhere, but no one took responsibility for the fault. To their credit, OCZ really stepped up and took care of their customers that were unhappy with their drives. Despite how completely irate they were at my article, they seemed to do the right thing after it was published. I can’t say the same for some of the other vendors.
The issue ended up being random write performance. These “affordable” MLC drives based on the JMicron controller were all tuned for maximum throughput. The sequential write speed of these drives could easily match and surpass that of the fastest hard drives.
If a company that had never made a hard drive before could come out with a product that on its first revision could outperform WD’s VelociRaptor and be more reliable thanks to zero moving parts...well, you get the picture. Optimize for sequential reads and writes!
The problem is that modern day OSes tend to read and write data very randomly, albeit in specific areas of the disk. And the data being accessed is rarely large, it’s usually very small on the order of a few KB in size. It’s these sorts of accesses that no one seemed to think about; after all these vendors and controller manufacturers were used to making USB sticks and CF cards, not hard drives.
| Sequential Read Performance | |
| JMicron JMF602B MLC | 134.7 MB/s |
| Western Digital VelociRaptor 300GB | 118 MB/s |
The chart above shows how much faster these affordable MLC SSDs were than the fastest 3.5” hard drive in sequential reads, but now look at random write performance:
| Random Write Latency | Random Write Bandwidth | |
| JMicron JMF602B MLC | 532.2 ms | 0.02 MB/s |
| Western Digital VelociRaptor 300GB | 7.2 ms | 1.63 MB/s |
While WD’s VelociRaptor averaged less than 8ms to write 4KB, these JMicron drives took around 70x that! Let me ask you this, what do you notice more - things moving very fast or things moving very slow?
The traditional hard drive benchmarks showed that these SSDs were incredible. The real world usage and real world tests disagreed. Storage Review was one of the first sites to popularize real world testing of hard drives nearly a decade ago. It seems that we’d all forgotten the lessons they taught us.
Random write performance is quite possibly the most important performance metric for SSDs these days. It’s what separates the drives that are worth buying from those that aren’t. All SSDs at this point are luxury items, their cost per GB is much higher than that of conventional hard drives. And when you’re buying a luxury anything, you don’t want to buy a lame one.
| Cost Per GB from Newegg.com | |
| Intel X25-E 32GB | $12.88 |
| Intel X25-M 80GB | $4.29 |
| OCZ Solid 60GB | $2.33 |
| OCZ Apex 60GB | $2.98 |
| OCZ Vertex 120GB | $3.49 |
| Samsung SLC 32GB | $8.71 |
| Western Digital Caviar SE16 640GB | $0.12 |
| Western Digital VelociRaptor 300GB | $0.77 |
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OCedHrt - Wednesday, March 18, 2009 - link
Excellent article. One of the best I've seen.cliffa3 - Wednesday, March 18, 2009 - link
I can tell a ton of work went into that, and all the history/details are greatly appreciated. I've been checking every week or so throughout February to see if it had been posted, but well worth the wait. As great as SSDs are, I can understand you not wanting to be near one for a while (-: Thanks for all the hard work...especially from the consumer standpoint. And kudos to OCZ for stepping up the way they did...that's (unfortunately) unheard of. Glad to see your no-compromise / report the facts no matter what attitude winning for the consumer. I'm glad at least one manufacturer was able to see (eventually) your intent wasn't to create a commotion, but to just plainly say what needed to be said.sngbrdb - Wednesday, March 18, 2009 - link
An extremely (as always) informative article; comprehensive and no angle missed. Good stuff!From an enthusiast's perspective, OCZ gained 10 levels of trust as a result of Ryan Peterson's response and handling of the Vertex' firmware. Ryan accepted the harsh reality expressed to him from an outside reviewer, risked marketability to rely on Anand's expertise (Anand is *absolutely* correct that 230MB/s is worthless if it comes with stuttering write latency), and resolved the problem in record time.
This is the rare kind of responsiveness and attitude that translate directly into sales (I'm on my way to price the Vertex now).
tshen83 - Wednesday, March 18, 2009 - link
BUT, still based on Windows Vista.I am going to drill this into reviewer's head -> NTFS isn't designed for SSDs.
There are three problems for properly reviewing SSDs today:
FileSystem, RAID controller, and SSD controller.
Each of them can compensate for the SSDs, the question is which one SHOULD be responsible for optimizing random IOs.
It is very clear that Intel's SSDs have implemented all the nitty gritty stuff like copy on write onto the SSD controller itself. So the OS or FileSystem shouldn't be responsible for performance degradation, however the same cannot be said for other SSDs.
I am sure results would be difference if this were conducted on Solaris/OpenSolaris ZFS with Adaptec 5405(IOP348 based RAID card). Not to pump Solaris and ZFS, but it is the primary reason why IBM wants to buy SUN, because it is the only File System on the market that can properly operate SSDs and to do so without RAID controllers.
If Anand really wants to stick to windows still, I think benchmarking on Windows 7 Beta would be slightly better option that Vista. Windows had made a lot of optimizations for rotational based hard disks that it actually makes SSD perform worse.
The Vertex random write 4K IOPS benchmark doesn't look right at 2.6MB/sec, that is hardly 650 IOs. It should be much higher. It could be the ICH10R controller though.
hyc - Wednesday, March 18, 2009 - link
I'd expect IBM's JFS to be pretty efficient on an SSD as well. Anything that appends and avoids overwriting existing sectors will perform better here.Stepping back a bit, I still have a perfectly usable Dothan-based laptop with IDE. Any chance of getting an in-depth review on recent Transcend 128GB IDE SSDs? My new laptop is running fine with a G.Skill Titan 256GB SSD, but when I fire up the older laptop it's unbearable, even with that 7200rpm Hitachi 100GB drive inside.
By the way, I paid under $2/GB for the 256GB G.Skill Titan; for the work I do with it on Linux it performs fine most of the time. (Just make sure to maximize use of the FS cache.) I don't see the value proposition for the OCZ Vertex or Summit.
tshen83 - Wednesday, March 18, 2009 - link
The random write 4K benchmark isn't right for the Vertex and other SSDs because of the test procedure:"The write test was performed over an 8GB range on the drive, while the read test was performed across the whole drive."
It partially disables any write optimization algorithms on the Vertex. Intel wasn't affected as much.
Anand, your first article pumping X25-M literally screwed Samsung's SSD manufacturers big time: they lost hundreds of millions of dollars because of your blatant pumping. Yes the random write was a big problem, but so was testing it on a Windows OS with NTFS and integrated SATA controller like ICH9/10 with no ram cache and obviously lack of IO optimizations for SSDs.
Please redo the review with a proper OS, ie Windows 7 beta or OpenSolaris.
Proteusza - Thursday, March 19, 2009 - link
Yeah, who in their right mind uses Windows and integrated SATA controllers? Oh wait, nearly everyone.Since its pretty obvious that you either work for Samsung or one of their partners, I think its laughable that you think this cost them hundreds of millions in sales. How big is the SSD market exactly, and how many potential buyers visit this site? Not enough to cause such an impact if you ask me.
And the fact remains - had you guys done what OCZ did, and optimized for real world use even if it cost you e-peen in the way of benchmarks, you would have been fine. Its only because you thought you could cheat and swindle consumers that you guys got a bad rep from Anand. Run an honest business, and your customers will thank you. I know that, if I ever considered an SSD, I would either buy Intel or an OCZ Vertex, nothing else. You know why? because they do what they say on the tin. You complain that the X25-M got a glowing review? Make a product as good as it and then Anand will sing your praises, but dont be upset when he tells it like it is.
tshen83 - Thursday, March 19, 2009 - link
Nearly everyone uses Windows and integrated SATA controllers. It still does not negate the fact that neither were optimized for SSD random IO patterns.No, I don't work for Samsung or its partners. It didn't cost them hundreds of millions in sales, but it did cost them hundreds of millions in inventory markdowns. Just look at the free falling of price of JMicron and original Samsung based SSDs in the past few months, and multiply by the inventory, that's the loss I was mentioning.
I am not saying that Intel X25-M is a bad drive. It is good. but there is no reason to use crippled OS File Systems and crippled SATA controller to show off the X25-M's internal copy on write features. When windows 7 comes out of beta(soon), it will be the OS the majority of people will use, and I am just looking forward 6 months when SSD adoption rate will improve more. As to Solaris ZFS, you don't need it if you aren't mentally capable of understanding its elegance.(Most people won't and it is ok)
strikeback03 - Thursday, March 19, 2009 - link
If they had also tested with Solaris/ZFS and reported that the drives worked well there, but 99.x% of users can't take advantage of that, would you have been happier? They may work perfectly well in that scenario, but it is meaningless to most users. Working properly in Vista and OSX is currently a requirement for selling to general consumers. Windows 7 was not even available in beta at the time of the last test, I would expect they will test with it once it launches but for now with the OS/FS they are likely to use most of the available SSDs fail.Also, your economic analysis assumes they would have been able to sell all their inventory at the inflated prices they wanted to. Whether or not they received a negative review from sites like Anandtech, word would have gotten out from early adopters that they had problems. Also, they would have moved fewer units at those prices.
tshen83 - Thursday, March 19, 2009 - link
I could really careless if they did review SSD ZFS. I am using it right now and it kicks ass. Next Version of OSX will have ZFS so I guess Apple agrees that ZFS is the way to go here.Vista is one of the crappiest OS Microsoft put out in recent memory, maybe besides the Windows ME release. Just look at Vista adoption rates, and you will see why.
You still don't understand my argument. My argument was that either File System, or RAID controller or SSD controller must implement copy on write.(basically if you have to erase a block to write to it, you are screwed) ZFS implements that in the file system. Adaptec 5 series or any Intel IOP RAID cards also help SSD performance greatly. If you don't use those two, then the SSD controller must implement it(X25-M is in this category.) You only need one of the three to properly handle SSDs to get greatly improved performance. Anandtech's review obviously skips file system optimization by picking Vista, and RAID controller optimization by picking ICH10R. What is left is the poor SSD controller that needs to virtualize the logical space, thus making the review entirely biased toward the X25-M for a good reason.
It is sad that this is supposedly a review for the Vertex units that OCZ sent to Anand, but it seems to me that it just turned out to be another article defending the X25-M. I know X25-M is a good SSD, but it does not explain why Anand should cripple the OS, Controller so much to do it and then test the SSDs with strange IO queue depth of 3 and during the random write IOPS test, tried to cap the write space to a 8GB confinement. Those settings greatly exaggerate X25-M's internal implementation advantages.
My economic analysis was based on SSD spot price published on dramexchange.com. Since the release of X25-M's review by Anandtech, all Samsung/JMicron MLC drives(Core, Core v2, Supertalent, etc) have been reduced to spot price of 2 dollars per GB to clear the inventories from the typical 4-5 dollars per GB that they used to command. The inventory markdown can be as high as 200+ dollar per drive and then you multiply that by the inventory that major vendors had, giving you hundreds of millions of dollars of aggregate damage sustained by the group of Samsung/JMicron partners.