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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  • korbendallas - Wednesday, March 18, 2009 - link

    If The implementation of the Trim command is as you described here, it would actually kind of suck.

    "The third step was deleting the original 4KB text file. Since our drive now supports TRIM, when this deletion request comes down the drive will actually read the entire block, remove the first LBA and write the new block back to the flash:"

    First of all, it would create a new phenomenon called Erase Amplification. This would negatively impact the lifetime of a drive.

    Secondly, you now have worse delete performance.


    Basically, an SSD 4kB block can be in 3 different states: erased, data, garbage. A block enters the garbage state when a block is "overwritten" or the Trim command marks the contents as invalid.

    The way i would imagine it working, marking block content as invalid is all the Trim command does.

    Instead the drive will spend idle time finding the 512kB pages with the most garbage blocks. Once such a page is found, all the data blocks from that page would be copied to another page, and the page would be erased. Doing it in this way maximizes the number of garbage blocks being converted to erased.
    Reply
  • alpha754293 - Wednesday, March 18, 2009 - link

    BTW...you might be able to simulate the drive as well using Cygwin where you go to the drive and run the following:

    $ dd if=/dev/random of=testfile bs=1024k count=76288

    I'm sure that you can come up with fancier shell scripts and stuff that uses the random number generator for the offsets (and if you really want it to work well, partition it so that when it does it, it takes up the entire initial 74.5 GB partition, and when you're done "dirtying" the data using dd and offset in a random pattern, grow the partition to take up the entire disk again.)

    Just as a suggestion for future reference.

    I use parts of that to some (varying) degree for when I do my file/disk I/O subsystem tests.
    Reply
  • nubie - Wednesday, March 18, 2009 - link

    I should think that most "performance" laptops will come with a Vertex drive in the near future.

    Finally a performance SSD that comes near mainstream pricing.

    Things are looking up, if more manufacturers get their heads out of the sand we should see prices drop as competition finally starts breeding excellence.
    Reply
  • GlItCh017 - Wednesday, March 18, 2009 - link

    I just wanted to comment that the backstory portion to this article is simply the most interesting part to an article (or almost even an article inside the main article). On top of that, it is easily the most interesting article I have ever read simply because of that section. Really really must say that I enjoyed reading it! Reply
  • radguy - Wednesday, March 18, 2009 - link

    I have been waiting for this one for a while and it was very informative. Thank you very much for it. I did pick up one of the patriot warp drives for my netbook. I was really happy until I installed avg free. So not running an antivirus on it anymore but I have drive image backup incase it goes bad. Overall pretty happy as it was only 80 bucks if I get my mir.
    I think I'm going to wait until windows 7 till I upgrade my primary desktop. 2 of those vertexs in raid 0 would be sweet though.
    Reply
  • sleepeeg3 - Wednesday, March 18, 2009 - link

    They were one of the first SSDs you reviewed and they use their own controller. How does their random write performance compare to everything else out now?

    These reviews made me totally reassess the purchase of the two Samsungs I bought. I had no idea the random writes on the Samsung drives were so bad. Other reviews show the Samsung drives doing better or at least near the X25-M in write tests: http://www.techreport.com/articles.x/15433/6">http://www.techreport.com/articles.x/15433/6 However, those tests probably would have been somewhat sequential.
    Reply
  • nubie - Wednesday, March 18, 2009 - link

    Grammatically awkward sentence on Page 21:

    "so if you own one of these drives - you owned a fixed version."

    The tense is incorrect (own/owned). I think "own a fixed version" is still awkward, perhaps "you have the fixed version", also the "so" may be superfluous. You can replace the ", so if" with a "; if". Here is how I might re-write the sentence:

    "The old firmware never shipped thanks to OCZ's quick acting; if you own one of these drives - you have a fixed version."

    (I am not an expert, so feel free to correct me if I am wrong.)


    Awesome article btw, thanks for setting me straight on SSD, I have been steering clear of them. I hope soon you can review SSD's and most are good to excellent. :)
    Reply
  • Flyboy27 - Wednesday, March 18, 2009 - link

    This article has answered every question I've had regarding SSDs recently. Thanks Anand! Reply
  • Flyboy27 - Wednesday, March 18, 2009 - link

    If a 120gb Vertex was around $250 I would get one yesterday. I suppose I can wait though. Reply
  • 7Enigma - Thursday, March 19, 2009 - link

    For me, 2 60's or 2 80's for around that price and I'm sold. Want the Raid0. Reply

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