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
Disappointed, I went back to OCZ
OCZ was worried. The last time I reviewed one of their SSDs I was truthful about it, and it hurt their sales considerably. Customers were returning drives, and to OCZ’s credit, they stepped up and even accepted some returns themselves - something that most manufacturers wouldn’t have done. Regardless what they had told me, there was some admission of fault there. Those JMicron drives were nothing short of crap.
As soon as OCZ started getting word that I wasn’t pleased with Vertex, they went into a state of panic. These drives all do very well in synthetic HDD tests like HDTach and ATTO, that’s generally all they’re reviewed in, so that’s all they’re tested in. But now OCZ was hearing that the Vertex wasn’t passing some of my tests and they had no idea what it was failing or why.
I tend to do a good job of keeping what tests I run secret until the review is published, so there isn’t any unfair optimization. I purposefully introduce new tests to our performance suites to help keep manufacturers honest and optimizing for real world usage scenarios rather than specific benchmarks. OCZ had no idea what I was running, but they knew that the Vertex wasn’t doing well.
Summit on the other hand was performing just fine, but that’s an expensive drive. Vertex was supposed to be good, it should’ve been good, there’s no reason for it to be performing this poorly. I ran the infamous iometer test to see what was going on:
| Iometer 4KB Random Writes, IOqueue=1, 8GB sector space | IOs per second | MB/s | Average Latency | Maximum Latency |
| Original Pre-release OCZ Vertex | 20.7 | 0.08 MB/s | 48.2 ms | 484.5 ms |
How on earth is this acceptable at all? Average latency of 48.2ms and a maximum latency as bad as the Apex and G.Skill Titan drives? I’ve heard some SSD vendors dismiss the iometer results but let me caution you against that. What these numbers are telling us is that on average, when your OS goes to write a 4KB file somewhere on your drive, it’ll take nearly 50ms. That’s 4.5x longer than a 5400 RPM 2.5” notebook drive and that’s the average case. What part of that sounds acceptable? Anyone who tells you otherwise is delusional.
I thought for sure that the drive was broken and that we’d made no progress since last fall. But the drive hadn’t launched yet, while there were glowing reviews of it, no one had wasted any money. I wrote an email to Ryan Petersen, OCZ’s CEO. I described my findings and told him that while the Vertex’s performance was better than any of the JMicron solutions, it was unacceptable for anything other than perhaps extremely light, single-tasking usage.
I told him it sucked. He said that wasn’t fair. We argued over email but he came back and asked me what I needed to see to make the drive better.
I told him I’d need an average response time in the sub-1ms range and a max latency no worse than Intel’s 94ms. I didn’t think it would be possible. I was prepared for OCZ to hate me once more. He told me to give him a couple of days.
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SunSetSupaNova - Wednesday, March 18, 2009 - link
Just wanted to say great job Anand on a great article, it took me a while to read it from start to finish but it was well worth it!FHDelux - Wednesday, March 18, 2009 - link
That was the best review i have read in a long time. I originally bought an OCZ Core drive when they first came out. It was the worst piece of garbage i had ever used. Newegg wouldn't let me send it back and OCZ support forums told me all sorts of junk to get me to fix it but it was just a poorly designed drive. I eventually ended up getting the egg to take it back for credit and i wrote OCZ off as a company blinded by the marketing department. I currently own an Intel SSD and its wonderfull, everytime i see OCZ statements saying their drive competes with the Intel drive i would laugh and think back to the OCZ techs telling me i need to update my bios, or i need to install vista service pack 1 before it would work right.I am thankful that you slapped that OCZ big wig around until they made a good product. All of us out there that wasted our time and money on Pre-vertex generation drives are greatfull to you and the whole industry should be kissing your butt right now.
One thing these companies need to learn is that marketing isn't the answer, creating solid products is. Hopefully OCZ has learned their lesson, and because of your article i will give them another chance.
THANK YOU!
kelstertx - Wednesday, March 18, 2009 - link
I didn't want to worry about eventual failure of the Flash chips of an SSD, and went with an SDRAM based Ramdrive from Acard. These drives have no latency of any kind, since they use SDRAM, and no lifespan of write cycles. I've been using mine for a couple of weeks now, and I like it a lot. I put Ubuntu on mine, and had 2G left for my small home folder. The standard HDD is my long-term storage for data files, music, etc. As SDRAM gets more affordable over time, I can add DIMMs and bump up the size.I know this review was about SSDs strictly, so an SDRAM drive doesn't technically fit, but it would have been interesting to see a 9010 or 9010b in there for comparison. It beat the Intel SSD in almost all the tests. http://techreport.com/articles.x/16255/1">http://techreport.com/articles.x/16255/1
7Enigma - Wednesday, March 18, 2009 - link
I've been eying these guys ever since the announced their first press release. Every time I always was drawn away by the constant need for power (4h max on battery scares the bejeezus out of me if I was to be gone on vacation during a storm), high power usage at all times, and high cost of entry (after factoring in all of the ram modules).I really dislike that article as well, since I think the bottlenecks were much less apparent with such a horribly slow cpu. The majority of that review's data is extremely compressed. I mean a P4, and 1 gig of memory; are you F'ing kidding me? This article was written in Jan of this year!? Why didn't they just use my old 486DX?
tirez321 - Wednesday, March 18, 2009 - link
What would a drive zeroing tool do to write performance, like if you used acronis privacy expert to zero only the "free space" regularly? Would it help write performance due to the drive not having to erase pages before writing?tirez321 - Wednesday, March 18, 2009 - link
I can kinda see that it wouldn't now.Because there would still be states there regardless.
But if you could inform the drive that it is deleted somehow, hmm.
strikeback03 - Wednesday, March 18, 2009 - link
The subjective experiences with stuttering are more important to me than most of the test numbers. Other tests I have found of the G.Skill Titan and similar have looked pretty good, but left out mention of stuttering in use.Too bad, as the 80GB Intel is too small and the ~$300 for a 120GB is about the most I am willing to pay. Maybe sometime this year the OCZ Vertex or similar will get there.
strikeback03 - Tuesday, March 24, 2009 - link
When I wrote that, the Newegg price for the 120GB Vertex was near $400. Now they have it for $339 with a $30 MIR. Now that's progress.kamikaz1k - Wednesday, March 18, 2009 - link
the latency times are switched...incase u wanted to kno.also, first post ^^ hallo!
GourdFreeMan - Wednesday, March 18, 2009 - link
It seems rather premature to assume the ATA TRIM command will significantly improve the SSD experience on the desktop. If you were to use TRIM to rewrite a nonempty physical block, you do not avoid the 2ms erase penalty when more data is written to that block later on and instead simply add the wear of another erase cycle. TRIM, then, is only useful for performance purposes when an entire 512 KiB physical block is free.A well designed operating system would have to keep track of both the physical and logical maps of used space on an SSD, and only issue TRIM when deletion of a logical cluster coincides with the freeing of an entire physical block. Issuing TRIMs at any other time would only hurt performance. This means the OS will have significantly fewer opportunities to issue TRIMs than you assume. Moreover, after significant usage the physical blocks will become fragmented and fewer and fewer TRIMs will be able to be issued.
TRIM works great as long as you only deal with large files, or batches of small files contiguously created and deleted with significant temporal locality. It would greatly aid SSDs in the "used" state Anand artificially creates in this article, but on a real system where months of web browsing, Windows updates and software installing/uninstalling have occurred the effect would be less striking.
TRIM could be mated with periodic internal (not filesystem) defragmentation to mitigate these issues, but that would significantly reduce the lifespan of the SSD...
It seems the real solution to the SSD performance problem would be to decrease the size of the physical block... ideally to 4 KiB, as that is the most common cluster size on modern filesystems. (This assumes, of course, that the erase, read and write latencies could be scaled down linearly.)