The SSD Relapse: Understanding and Choosing the Best SSD
by Anand Lal Shimpi on August 30, 2009 12:00 AM EST- Posted in
- Storage
Tying it All Together: SSD Performance Degradation
More spare area is better for random workloads, but desktop workloads aren’t random enough to justify setting aside more spare area to improve performance; most reviews don’t test in a used state, and more users would simply flock to lower price-per-GB drives with less spare area.
Drives that drop the most in performance from new to used state have the most to gain from the TRIM instruction. Depending on how you use your drive of course:
| % Performance Drop in Used State vs. New State | |||
| 4KB Random Write | 2MB Sequential Write | PCMark Vantage HDD Suite | |
| Intel X25-E 64GB (SLC) | 26.1% | 5.4% | 9.7% |
| Intel X25-M G1 160GB (MLC) | 35.5% | 3.8% | 16.7% |
| Intel X25-M G2 160GB (MLC) | 0.7% | 2.2% | 15.3% |
| OCZ Agility 128GB (Indilinx MLC) | 44.8% | 15.0% | 4.4% |
| OCZ Summit 256GB (Samsung MLC) | 72.4% | 3.0% | 23.6% |
| OCZ Vertex EX 128GB (Indilinx SLC) | 60.5% | 20.8% | 0.8% |
| OCZ Vertex Turbo 128GB (Indilinx MLC) | 44.0% | 15.4% | 4.5% |
| Patriot Torqx 128GB (Indilinx MLC) | 44.6% | 15.6% | 3.5% |
Depending on the scenario, all three controllers have a lot to gain from TRIM. Random write performance drops significantly for almost every single drive. The worst is the Samsung RBB controller, which lost over 70% of its performance between new and used states; Samsung needs TRIM.
Intel made some significant improvements going from the G1 to G2 drives, the new drive loses no performance in our random write test. This is thanks to firmware tweaks and having twice as much DRAM to track data in; the more data the Intel drive can keep track of, the better it is at organization, management and garbage collection. From a pure performance standpoint, the G2 might actually be better for server workloads than the X25-E. In terms of lifespan however, the X25-E has the G2 beat.
Only the Indilinx drives lose an appreciable amount of performance in the sequential write test, but they are the only drives to not lose any performance in the more real-world PCMark Vantage HDD suite. Although not displayed here, the overall PCMark Vantage score takes an even smaller hit on Indilinx drives. This could mean that in the real world, Indilinx drives stand to gain the least from TRIM support. This is possibly due to Indilinx using a largely static LBA mapping scheme; the only spare area is then the 6.25% outside of user space regardless of how used the drive is.
Both Samsung and Intel have a lot to gain from TRIM. Samsung’s performances goes from utterly unacceptable to reasonable (but not price justified) with TRIM. Intel’s performance goes from class-leading to more, er, class-leading.
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Anand Lal Shimpi - Monday, August 31, 2009 - link
wow I misspelled my own name :) Time to sleep for real this time :)Take care,
Anand
IntelUser2000 - Monday, August 31, 2009 - link
Looking at pure max TDP and idle power numbers and concluding the power consumption based on those figures are wrong.Look here: http://www.anandtech.com/cpuchipsets...px?i=3403&a...">http://www.anandtech.com/cpuchipsets...px?i=3403&a...
Modern drives quickly reach idle even between times where the user don't even know and at "load". Faster drives will reach lower average power because it'll work faster to get to idle. This is why initial battery life tests showed X25-M with much higher active/idle power figures got better battery life than Samsungs with less active/idle power.
Max power is important, but unless you are running that app 24/7 its not real at all, especially the max power benchmarks are designed to reach close to TDP as possible.
Anand Lal Shimpi - Monday, August 31, 2009 - link
I agree, it's more than just max power consumption. I tried to point that out with the last paragraph on the page:"As I alluded to before, the much higher performance of these drives than a traditional hard drive means that they spend much more time at an idle power state. The Seagate Momentus 5400.6 has roughly the same power characteristics of these two drives, but they outperform the Seagate by a factor of at least 16x. In other words, a good SSD delivers an order of magnitude better performance per watt than even a very efficient hard drive."
I didn't have time to run through some notebook tests to look at impact on battery life but it's something I plan to do in the future.
Take care,
Anand
IntelUser2000 - Monday, August 31, 2009 - link
Thanks, people pay too much attention to just the max TDP and idle power alone. Properly done, no real apps should ever reach max TDP for 100% of the duration its running at.cristis - Monday, August 31, 2009 - link
page 6: "So we’re at approximately 36 days before I exhaust one out of my ~10,000 write cycles. Multiply that out and it would take 36,000 days" --- wait, isn't that 360,000 days = 986 years?Anand Lal Shimpi - Monday, August 31, 2009 - link
woops, you're right :) Either way your flash will give out in about 10 years and perfectly wear leveled drives with no write amplification aren't possible regardless.Take care,
Anand
cdillon - Monday, August 31, 2009 - link
I gather that you're saying it'll give out after 10 years because a flash cell will lose its stored charge after about 10 years, not because the write-life will be surpassed after 10 years, which doesn't seem to be the case. The 10-year charge life doesn't mean they become useless after 10 years, just that you need to refresh the data before the charge is lost. This makes flash less useful for data archival purposes, but for regular use, who doesn't re-format their system (and thus re-write 100% of the data) at least once every 10 years? :-)Zheos - Monday, August 31, 2009 - link
"This makes flash less useful for data archival purposes, but for regular use, who doesn't re-format their system (and thus re-write 100% of the data) at least once every 10 years? :-)"I would like an input on that too, cuz thats a bit confusing.
GourdFreeMan - Tuesday, September 1, 2009 - link
Thermal energy (i.e. heat) allows the electrons trapped in the floating gate to overcome the potential well and escape, causing zeros (represented by a larger concentration of electrons in the floating gate) to eventually become ones (represented by a smaller concentration of electrons in the floating gate). Most SLC flash is rated at about 10 years of data retention at either 20C (68F) or 25C (77F). What Anand doesn't mention is that as a rule of thumb for every 9 degrees C (~16F) that the temperature is raised above that point, data retention lifespan is halved. (This rule of thumb only holds for human habitable temperatures... the exact relation is governed by the Arrhenius equation.)Wear leveling and error correction codes can be employed to mitigate this problem, which only gets worse as you try to store more bits per cell or use a smaller lithography process without changing materials or design.
Zheos - Tuesday, September 1, 2009 - link
Thank you GourdFreeMan for the additional input,But, if we format like every year or so , doesnt the countdown on data retention restart from 0 ? or after ~10 year (seems too be less if like you said temperature affect it) the SSD will not only fail at times but become unusable ? Or if we come to that point a format/reinstall would resolve the problem ?
I dont care about losing data stored after 10 years, what i do care is if the drive become ASSURELY unsusable after 10 year maximum. For drives that comes at a premium price, i don't like this if its the case.