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
Why You Should Want an SSD
For the past several months I’ve been calling SSDs the single most noticeable upgrade you can do to your computer. Whether desktop or laptop, stick a good SSD in there and you’ll notice the difference.
I’m always angered by the demos in any Steve Jobs keynote. Not because the demos themselves are somehow bad, but because Jobs always has a perfectly clean machine to run the demos on - and multiple machines at that. Anyone who has built a computer before knows the glory of a freshly installed system; everything just pops up on your screen. Applications, windows, everything - the system is just snappy.
Of course once you start installing more applications and have more things running in the background, your system stops being so snappy and you tend to just be thankful when it doesn’t crash.
A big part of the problem is that once you have more installed on your system, there are more applications sending read/write requests to your IO subsystem. While our CPUs and GPUs thrive on being fed massive amounts of data in parallel, our hard drives aren’t so appreciative of our multitasking demands. And this is where SSDs truly shine.
Before we go too far down the rabbit hole I want to share a few numbers with you.
This is Western Digital’s VelociRaptor. It’s a 300GB drive that spins its platters at 10,000RPM and is widely considered the world’s fastest consumer desktop hard drive.
The 300GB VelociRaptor costs about $0.77 per GB.
This is the Intel X25-M. The Conroe of the SSD world, the drive I reviewed last year. It costs about $4.29 per GB; that’s over 5x the VelociRaptor’s cost per GB.
The VelociRaptor is the dominant force in the consumer HDD industry and the X25-M is the svelte bullfighter of the SSD world.
Whenever anyone mentions a more affordable SSD you always get several detractors saying that you could easily buy 2 VelociRaptors for the same price. Allow me to show you one table that should change your opinion.
This is the Average Read Access test from Lavalys’ Everest Disk benchmark. The test simply writes a bunch of files at random places on the disk and measures how long it takes to access the files.
Measuring random access is very important because that’s what generally happens when you go to run an application while doing other things on your computer. It’s random access that feels the slowest on your machine.
| Random Read Latency in ms | |
| Intel X25-M | 0.11 ms |
| Western Digital VelociRaptor | 6.83 ms |
The world’s fastest consumer desktop hard drive, Western Digital’s 300GB VelociRaptor can access a random file somewhere on its platters in about 6.83ms; that’s pretty quick. Most hard drives will take closer to 8 or 9ms in this test. The Intel X25-M however? 0.11ms. The fastest SSDs can find the data you’re looking for in around 0.1ms. That’s an order of magnitude faster than the fastest hard drive on the market today.
The table is even more impressive when you realize that wherever the data is on your SSD, the read (and write) latency is the same. While HDDs are fastest when the data you want is in the vicinity of the read/write heads, all parts of a SSD are accessed the same way. If you want 4KB of data, regardless of where it is, you’ll get to it at the same speed from a SSD.
The table below looks at sequential read, sequential write and random write performance of these two kings of their respective castles. The speeds are in MB/s.
| Sequential Read (2MB Block) | Sequential Write (2MB Block) | Random Write (4KB Block) | |
| Intel X25-M | 230 MB/s | 71 MB/s | 23 MB/s |
| Western Digital VelociRaptor | 118 MB/s | 119 MB/s | 1.6 MB/s |
If you’re curious, these numbers are best case scenario for the VelociRaptor and worst case scenario for the X25-M (I’ll explain what that means later in the article). While the VelociRaptor is faster in the large block sequential writes look at the sequential read and random write performance. The X25-M destroys the VelociRaptor in sequential reads and is an order of magnitude greater in random write performance. If you’re curious, it’s the random write performance that you’re most likely to notice and that’s where a good SSD can really shine; you write 4KB files far more often than you do 2MB files while using your machine.
If the table above doesn’t convince you, let me share one more datapoint with you. Ever play World of Warcraft? What we’re looking at here is the amount of time it takes to get from the character selection screen into a realm with everything loaded. This is on a fully configured system with around 70GB of applications and data as well as real time anti-virus scanning going on in the background on every accessed file.
| WoW Enter Realm Time in Seconds | |
| Intel X25-M | 4.85 s |
| Western Digital VelociRaptor | 12.5 s |
The world’s fastest hard drive gets us into the game in 12.5 seconds. The Intel X25-M does it in under 5.
SSDs make Vista usable. It doesn’t matter how much background crunching the OS is doing, every application and game launches as if it were the only thing running on the machine. Everything launches quickly. Much faster than on a conventional hard drive. If you have the ability, try using your system with a SSD for a day then go back to your old hard drive; if that test doesn’t convince you, nothing will.
That’s just a small taste of why you’d want an SSD, now let’s get back to finding a good one.
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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.