New vs Used SSD Performance

We begin our look at how the overhead of managing pages impacts SSD performance with iometer. The table below shows iometer random write performance; there are two rows for each drive, one for “new” performance after a secure erase and one for “used” performance after the drive has been well used.

4KB Random Write Speed New "Used"
Intel X25-E   31.7 MB/s
Intel X25-M 39.3 MB/s 23.1 MB/s
JMicron JMF602B MLC 0.02 MB/s 0.02 MB/s
JMicron JMF602Bx2 MLC 0.03 MB/s 0.03 MB/s
OCZ Summit 12.8 MB/s 0.77 MB/s
OCZ Vertex 8.2 MB/s 2.41 MB/s
Samsung SLC 2.61 MB/s 0.53 MB/s
Seagate Momentus 5400.6 0.81 MB/s -
Western Digital Caviar SE16 1.26 MB/s -
Western Digital VelociRaptor 1.63 MB/s -

 

Note that the “used” performance should be the slowest you’ll ever see the drive get. In theory, all of the pages are filled with some sort of data at this point.

All of the drives, with the exception of the JMicron based SSDs went down in performance in the “used” state. And the only reason the JMicron drive didn’t get any slower was because it is already bottlenecked elsewhere; you can’t get much slower than 0.03MB/s in this test.

These are pretty serious performance drops; the OCZ Vertex runs at nearly 1/4 the speed after it’s been used and Intel’s X25-M can only crunch through about 60% the IOs per second that it did when brand new.

So are SSDs doomed? Is performance going to tank over time and make these things worthless?


"Used" SSD performance vs. conventional hard drives.

Pay close attention to the average write latency in the graph above. While Intel’s X25-M pulls an extremely fast sub-0.3ms write latency normally, it levels off at 0.51ms in its used mode. The OCZ Vertex manages a 1.43ms new and 4.86ms used. There’s additional overhead for every write but a well designed SSD will still manage extremely low write latencies. To put things in perspective, look at these drives at their worst compared to Western Digital’s VelociRaptor.The degraded performance X25-M still completes write requests in around 1/8 the time of the VelociRaptor. Transfer speeds are still 8x higher as well.

Note that not all SSDs see their performance drop gracefully. The two Samsung based drives perform more like hard drives here, but I'll explain that tradeoff much later in this article.

How does this all translate into real world performance? I ran PCMark Vantage on the new and used Intel drive to see how performance changed.

PCMark Overall Score New "Used" % Drop
Intel X25-M 11902 11536 3%
OCZ Summit 10972 9916 9.6%
OCZ Vertex 11253 9836 14.4%
Samsung SLC 10143 9118 10.1%
Seagate Momentus 5400.6 6817 - -
Western Digital VelociRaptor 7500 - -

 

The real world performance hit varies from 0 - 14% depending on the drive. While the drives are still faster than a regular hard drive, performance does drop in the real world by a noticeable amount. The trim command would keep the drive’s performance closer to its peak for longer, but it would not have prevented this from happening.

PCMark Vantage HDD Test New "Used" % Drop
Intel X25-M 29879 23252 22%
JMicron JMF602Bx2 MLC 11613 11283 3%
OCZ Summit 25754 16624 36%
OCZ Vertex 20753 17854 14%
Samsung SLC 17406 12392 29%
Seagate Momentus 5400.6 3525 -  
Western Digital VelociRaptor 6313 -  

 

HDD specific tests show much more severe drops, ranging from 20 - 40% depending on the drive. Despite the performance drop, these drives are still much faster than even the fastest hard drives.

Simulating a Used Drive SSD Aging: Read Speed is Largely Unaffected
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  • Glenn - Wednesday, March 18, 2009 - link

    tshen83 "A very thorough review by tshen83, an hour ago
    BUT, still based on Windows Vista.
    "

    As long as these drives are marketed toward said OS, why would you not use it? Most of us wouldn't recognize Solaris if we saw it! And I believe you seriously overestimate yourself if your gonna drill anything into Anands head! You might need your own site, huh?

    Great Job Anand! Don't forget to remind these CEO's that they also need to provide any software needed to configure and optimize these drives to work properly. ie go to OCZ Forums and try to figure out how to align, optimize and keep your drive running like it's supposed to, in less than 4 hours of reading! It would be nice if these companies would do their own beta testing and not rely on early adopters to do it for them!
    Reply
  • Roland00 - Wednesday, March 18, 2009 - link

    It was a joy to read all 31 pages Reply
  • MagicPants - Wednesday, March 18, 2009 - link

    Anand it would be really helpful to have a list of SSD companies blacklisting you so I know which ones to avoid. In general it would be nice to know who doesn't provide review samples to reputable sites. Reply
  • Jamor - Wednesday, March 18, 2009 - link

    The best tech article I've ever read, and I've read a few. Reply
  • haze4peace - Wednesday, March 18, 2009 - link

    Wow, excellent article and so much useful information in an easy to understand way. I have just recently been paying attention to SSDs and thanks to this article I am armed with the information to make the correct choice for my needs. Thanks AnandTech, its the deep and honest articles like these that keep me coming back for more. Reply
  • Alseki - Wednesday, March 18, 2009 - link

    I just registered then simply to say, great article. Really informative and enjoyable to read. Reply
  • alexsch8 - Wednesday, March 18, 2009 - link

    Anand,

    Thank you for this article, very informative.

    Looking at the example you are giving with your self-manufactured SSD drive: If I save the DOC I use up a page. Based on what you are saying, if I make a change to that DOC, it would then be saved in the next page instead of overwriting the existing page? If that is true, then the File Allocation system (FAT or MFT) itself would contribute quite a bit to the 'filling up of pages' phenomena. Could you elaborate if the proposed file system for SSD addresses this?
    Reply
  • Ytterbium - Wednesday, March 18, 2009 - link

    Fantastic article, shame that the vendors blacklisted you for telling the truth and OCZ rock for working so hard to address issues.

    I'll be ordering my Intel SSD soon, I'll defintly consider the Summit when it comes out for my encoding rig as there sequental writes matter to me.
    Reply
  • mindless1 - Wednesday, March 18, 2009 - link

    Great even, but I've have to disagree with the significance of the passage that suggested the Indilinx controller makes data loss as bad on those SSD as on a conventional hard drive.

    The primary cause of data loss is mechanical or component failure, not power loss. If we want to consider power loss, it's not just the drive which is prone to lose data, the entire system memory suffers far more data loss than that.

    Further, a sufficiently sized supercapacitor should keep the drive operating for a period of time beyond when the rest of the system would be operational, it could be sufficient for the controller to finish writing to flash all received data (or just use an UPS, that's what they're for?).

    Second, I can't believe that OCZ only tests designs with HDTach and Atto, I think it more likely they knew of the problem but didn't expect anyone to find it so quickly, and felt the higher sequential speeds made it more marketable. This makes me feel that manufacturers, then online sellers should differentiate their drives with a standardized random read/write score.

    What would be really nice is if the Indilinx based SSDs had an application available, similar to a HDD acoustic management bit changing app, that lets the owner set their own preference for IO versus sequential read performance.
    Reply
  • gomakeit - Wednesday, March 18, 2009 - link

    This is by far the BEST article on SSD I've ever read! Great job anand and yes I read every single word of it! Reply

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