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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SkullOne - Wednesday, March 18, 2009 - link
Fantastic article. Definitely one of the best I've read in a long time. Incredibly informative. Everyone who reads this article is a little bit smarter afterwards.All the great information about SSDs aside, I think the best part though is how OCZ is willing to take blame for failure earlier and fix the problems. Companies like that are the ones who will get my money in the future especially when it is time for me to move from HDD to SSD.
Apache2009 - Wednesday, March 18, 2009 - link
i got one Vertex SSD. Why suspend will cause system halt ? My laptop is nVidia chipset and it is work fine with HDD. Somebody know it ?MarcHFR - Wednesday, March 18, 2009 - link
Hi,You wrote that there is spare-area on X25-M :
"Intel ships its X25-M with 80GB of MLC flash on it, but only 74.5GB is available to the user"
It's a mistake. 80 GB of Flash look like 74.5GB for the user because 80,000,000,000 bytes of flash is 74.5 Go for the user point of view (with 1 KB = 1024 byte).
You did'nt point out the other problem of the X25-M : LBA "optimisation". After doing a lot of I/O random write the speed in sequential write can get down to only 10 MB /s :/
Kary - Thursday, March 19, 2009 - link
The extra space would be invisible to the end user (it is used internally)Also, addressing is normally done in binary..as a result actual sizes are typically in binary in memory devices (flash, RAM...):
64gb
128gb
80 GB...not compatible with binary addressing
(though 48GB of a 128GB drive being used for this seems pretty high)
ssj4Gogeta - Wednesday, March 18, 2009 - link
Did you bother reading the article? He pointed out that you can get any SSD (NOT just Intel's) stuck into a situation when only a secure erase will help you out. The problem is not specific to Intel's SSD, and it doesn't occur during normal usage.MarcHFR - Wednesday, March 18, 2009 - link
The problem i've pointed out has nothing to do with the performance dregradation related to the write on a filled page, it's a performance degradation related to an LBA optimisation that is specific to Intel SSD.VaultDweller - Wednesday, March 18, 2009 - link
So where would Corsair's SSD fit into this mix? It uses a Samsung MLC controller... so would it be comparable to the OCZ Summit? I would expect not since the rated sequential speeds on the Corsair are tremendously lower than the Summit, but the Summit is the closest match in terms of the internals.kensiko - Wednesday, March 18, 2009 - link
No, OCZ Summit = newest Samsung controller. The Corsair use the previous controller, smaller performance.VaultDweller - Wednesday, March 18, 2009 - link
So what's the difference?The Summit is optimized for sequential performance at the cost of random I/O, as per the article. That is clearly not the case with the Corsair drive, so how does the Corsair hold up in terms of random I/O? That's what I'm interested in, since the sequential on the Corsair is "fast enough" if the random write performance is good.
jatypc - Wednesday, March 18, 2009 - link
A detailed description of how SSDs operate makes me wonder: Imagene hypothetically I have a SSD drive that is filled from more than 90% (e.g., 95%) and those 90% are read-only things (or almost read-only things such as exe and other application files). The remaining 10% is free or frequently written to (e.g., page/swap file). Then the use of drive results - from what I understood in the article - in very fast aging of those 10% of the SSD disk because the 90% are occupied by read-only stuff. If the disk in question has for instance 32GB, those 10% are 3.2 GB (e.g., a size of a usual swap file) and after writing it approx. 10000 times, the respective part of the disk would become dead. Being occupies by a swap file, this number of reads/writes can be achieved in one or two years... Am I right?