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
The Verdict
There’s no skirting the issue: even the best SSDs lose performance the more you use them. Eventually their performance should level off but what matters the most is how their performance degrades.
In using the X25-M I’d say that the performance drop was noticeable but not a deal breaker - and the data tends to agree with me. With average write latencies still well under 1ms, the drive maintained its most important performance characteristic - the ability to perform random accesses much faster than a conventional hard drive.
Keep in mind that with the cost per GB being as high as it is, these SSDs aren’t going to be used for large file storage in a desktop or notebook. You’re far more likely to use one as your boot/applications drive. As such, what matter the most aren’t peak transfer rates but rather fast access times. On a well designed drive with a good controller, peak transfer rates may fall over time, but latency remains good.
You end up with a drive that still manages to be much faster than the fastest 3.5” hard drives, but slower than when you first got it.
If, however, you aren’t ok with the performance drop over time then it’s worth considering what your options will be. When drives ship with ATA-TRIM support, hopefully late this year, they will do a better job of staying closer to their maximum performance. But the problem won’t be solved completely. Instead, what we’ll need to see is a more fundamental architectural change to eliminate the problem.
I still believe that a SSD is the single most effective performance upgrade you can do to your PC; even while taking this behavior into account. While personally I wouldn’t give up a SSD in any of my machines, I can understand the hesitation in investing a great deal of money in one today.
Intel’s X25-M: Not So Adaptive Performance?
The Intel drive is in a constant quest to return to peak performance, that’s what its controller is designed to do. The drive is constantly cleaning as it goes along to ensure its performance is as high as possible, for as long as possible. A recent PC Perspective investigation unearthed a scenario where the X25-M is unable to recover and is stuck at a significantly lower level of performance until the drive is secure erased once more.
There’s not much I can say about the issue other than I’ve been working with Intel on it very closely and it’s not something I’m overly concerned about at this point. I can replicate the PC Perspective data but not by using my machine normally. Through the right combination of benchmarks I can effectively put the drive in a poor performance state that it won’t recover from without a secure erase. I should also mention that I can do the same to other drives as well.
I’ll be able to say more soon but for now just hang tight. I’d venture a guess that Intel would not leave its most loyal customers out in the cold after spending $400 - $800 on a SSD. I can’t speak for Intel but like I said, stay tuned.
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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?