The SSD Relapse: Understanding and Choosing the Best SSD
by Anand Lal Shimpi on August 30, 2009 12:00 AM EST- Posted in
- Storage
One Tough Act to Follow
What have I gotten myself into? The SSD Anthology I wrote back in March was read over 2 million times. Microsoft linked it, Wikipedia linked it, my esteemed colleagues in the press linked it, Linus freakin Torvalds linked it.
The Anthology took me six months to piece together; I wrote and re-wrote parts of that article more times than I'd care to admit. And today I'm charged with the task of producing its successor. I can't do it.
The article that started all of this was the Intel X25-M review. Intel gave me gold with that drive; the article wrote itself, the X25-M was awesome, everything else in the market was crap.
Intel's X25-M SSDs: The drives that started a revolution
The Anthology all began with a spark: the SSD performance degradation issue. It took a while to put together, but the concept and the article were handed to me on a silver platter: just use an SSD for a while and you’ll spot the issue. I just had to do the testing and writing.
OCZ's Vertex: The first Indilinx drive I reviewed, the drive that gave us hope there might be another.
But today, as I write this, the words just aren't coming to me. The material is all there, but it just seems so mature and at the same time, so clouded and so done. We've found the undiscovered country, we've left no stone unturned, everyone knows how these things work - now SSD reviews join the rest as a bunch of graphs and analysis, hopefully with witty commentary in between.
It's a daunting, no, deflating task to write what I view as the third part in this trilogy of articles. JMicron is all but gone from the market for now, Indilinx came and improved (a lot) and TRIM is nearly upon us. Plus, we all know how trilogies turn out. Here's hoping that this one doesn't have Ewoks in it.
What Goes Around, Comes Around
No we're not going back to the stuttering crap that shipped for months before Intel released their X25-M last year, but we are going back in the way we have to look at SSD performance.
In my X25-M review the focus was on why the mainstream drives at the time stuttered and why the X25-M didn't. Performance degradation over time didn't matter because all of the SSDs on the market were slow out of the box; and as I later showed, the pre-Intel MLC SSDs didn’t perform worse over time, they sucked all of the time.
Samsung and Indilinx emerged with high performance, non-stuttering alternatives, and then we once again had to thin the herd. Simply not stuttering wasn't enough, a good SSD had to maintain a reasonable amount of performance over the life of the drive.
The falling performance was actually a side effect of the way NAND flash works. You write in pages (4KB) but you can only erase in blocks (128 pages or 512KB); thus SSDs don't erase data when you delete it, only when they run out of space to write internally. When that time comes, you run into a nasty situation called the read-modify-write. Here, even to just write 4KB, the controller must read an entire block (512KB), update the single page, and write the entire block back out. Instead of writing 4KB, the controller has to actually write 512KB - a much slower operation.
I simulated this worst case scenario performance by writing to every single page on the SSDs I tested before running any tests. The performance degradation ranged from negligible to significant:
| PCMark Vantage HDD Score | New | "Used" |
| Corsair P256 (Samsung MLC) | 26607 | 18786 |
| OCZ Vertex Turbo (Indilinx MLC) | 26157 | 25035 |
So that's how I approached today's article. Filling the latest generations of Indilinx, Intel and Samsung drives before testing them. But, my friends, things have changed.
The table below shows the performance of the same drives showcased above, but after running the TRIM instruction (or a close equivalent) against their contents:
| PCMark Vantage HDD Score | New | "Used" | After TRIM/Idle GC | % of New Perf |
| Corsair P256 (Samsung MLC) | 26607 | 18786 | 24317 | 91% |
| OCZ Vertex Turbo (Indilinx MLC) | 26157 | 25035 | 26038 | 99.5% |
Oh boy. I need a new way to test.
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zodiacfml - Wednesday, September 2, 2009 - link
Very informative, answered more than anything in my mind. Hope to see this again in the future with these drive capacities around $100.mgrmgr - Wednesday, September 2, 2009 - link
Any idea if the (mid-Sept release?) OCZ Colossus's internal RAID setup will handle the problem of RAID controllers not being able to pass Windows 7's TRIM command to the SSD array. I'm intent on getting a new Photoshop machine with two SSDs in Raid-0 as soon as Win7 releases, but the word here and elsewhere so far is that RAID will block the TRIM function.kunedog - Wednesday, September 2, 2009 - link
All the Gen2 X-25M 80GB drives are apparently gone from Newegg . . . so they've marked up the Gen1 drives to $360 (from $230):http://www.newegg.com/Product/Product.aspx?Item=N8...">http://www.newegg.com/Product/Product.aspx?Item=N8...
Unbelievable.
gfody - Wednesday, September 2, 2009 - link
What happened to the gen2 160gb on Newegg? For a month the ETA was 9/2 (today) and now it's as if they never had it in the first place. The product page has been removed.It's like Newegg are holding the gen2 drives hostage until we buy out their remaining stock of gen1 drives.
iwodo - Tuesday, September 1, 2009 - link
I think it acts as a good summary. However someone wrote last time about Intel drive handling Random Read / Write extremely poorly during Sequential Read / Write.Has Aanand investigate yet?
I am hoping next Gen Intel SSD coming in Q2 10 will bring some substantial improvement.
statik213 - Tuesday, September 1, 2009 - link
Does the RAID controller propagate TRIM commands to the SSD? Or will having RAID negate TRIM?justaviking - Tuesday, September 1, 2009 - link
Another great article, Anand! Thanks, and keep them coming.If this has already been discussed, I apologize. I'm still exhausted from reading the wonderful article, and have not read all 17 pages of comments.
On PAGE 3, it talks about the trade-off of larger vs. smaller pages.
I wonder if it would be feasible to make a hybrid drive, with a portion of the drive using small pages for faster performance when writing small files, and the majority of it being larger pages to keep the management of the drive reasonable.
Any file could be written anywhere, but the controller would bias small writes to the small pages, and large writes to large files.
Externally it would appear as a single drive, of course, but deep down in the internals, it would essentially be two drives. Each of the two portions would be tuned for maximum performance in different areas, but able to serve as backup or overflow if the other portion became full or ever got written to too many times.
Interesting concept? Or a hair brained idea buy an ignorant amateur?
CList - Tuesday, September 1, 2009 - link
Great article, wonderful to see insightful, in depth analysis.I'd be curious to hear anyone's thoughts on the implications are of running virtual hard disk files on SSD's. I do a lot of work these days on virtual machines, and I'd love to get them feeling more snappy - especially on my laptop which is limited to 4GB of ram.
For example;
What would the constant updates of those vmdk (or "vhd") files do to the disk's lifespan?
If the OS hosting the VM is windows 7, but the virtual machine is WinServer2003 will the TRIM command be used properly?
Cheers,
CList
pcfxer - Tuesday, September 1, 2009 - link
Great article!"It seems that building Pidgin is more CPU than IO bound.."
Obviously, Mr. Anand doesnt' understand how compilers work ;). Compilers will always be CPU and memory bound, reduce your memory in the computer to say 256MB (or lower) and you'll see what I mean. The levels of recursion necessary to follow the production (grammars that define the language) use up memory but would rarely use the drive unless the OS had terrible resource management. :0.
CMGuy - Wednesday, September 2, 2009 - link
While I can't comment on the specifics of software compilers I know that faster disk IO makes a big difference when your performing a full build (compilation and packaging) of software.IDEs these days spend a lot their time reading/writing small files (thats a lot of small, random, disk IO) and a good SSD can make a huge difference to this.