Simulating a Used Drive

Since SSD performance degrades over time, it’s important to not only look at how well these drives perform new - but also the worst they’d perform over their lifetime. In order to do so we’d need a repeatable way of “seasoning” a drive to reduce its performance to the worst it could possibly get. The most realistic worst-case scenario is one where every single block on the drive is full of data. If a secure erase wipes all LBAs, that’s the best place to start. To simulate a well seasoned drive I first secure erased the drive.

After the secure erase, I used iometer to write one contiguous file across the disk - filling up the entire drive with 128KB blocks. In the case of the 80GB Intel X25-M, that’s 74.5GB of data on the drive before I run a single benchmark. The spare area is left untouched.

Next, I take my test image and I restore it onto the partition with a sector by sector copy. The sequential file write made sure that data is stored in every page of the SSD, the test image restore adds a twist of randomness (and realism) to the data.

There are other ways to produce a drive in its well-used state, but this ends up being the most consistent and repeatable. To confirm that my little simulation does indeed produce a realistically worn drive I ran PCMark on three different drives: 1) a freshly secure-erased Intel X25-M, 2) an Intel X25-M setup using the method I just described and 3) the Intel X25-M used in my CPU testbed that has been through hundreds of SYSMark runs.

The benchmark of choice is PCMark Vantage; it simulates the real world better than most drive benchmarks. The results are below:

Intel X25-M State PCMark Vantage Overall Test PCMark Vantage HDD Test
Fresh Secure Erase 11902 29879
Simulated Used Drive 11536 23252
Actual Testbed Used Drive 11140 23438

 

The secure erased system loses about 3% of its overall performance and 22% of its hard drive specific performance compared to my testbed drive. The seasoning method I described above produces a drive with nearly identical drops in performance.

The method appears to be sound.

Now that we have a way of simulating a used drive, let’s see how the contestants fared.

Restoring Your Drive to Peak Performance New vs Used SSD Performance
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  • KadensDad - Tuesday, October 27, 2009 - link

    How do these drives fail? I have heard that they will just suddenly die, no more writes or reads possible. What I would like to know is what happens when it dies? Do you lose all data? Just can't write anymore? How does the OS respond? Any early warnings? What about e.g. CRC? How does possibility of data corruption compare to traditional SSD? What about RAID? Since the drives are electrical, not mechanical, this reduces the number of failure vectors and environmental concerns (e.g., ambient temperature over lifetime of the drive). Won't SSDs therefore fail closer together in time in a RAID configuration? This reduces the window of opportunity for fixing an array and also decreases the applicability of RAID, however marginal.
    Reply
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  • adsmith82 - Monday, September 14, 2009 - link

    I need to run HDDErase on an X25-M. No matter what bootable CD or flash drive I create, HDDErase does not see either of my SATA hard drives. I already disabled AHCI in BIOS. Also, I am using version 3.3. I know that 4.0 does not work with the X25-M.

    Can someone help me troubleshoot this please? Thanks.
    Reply
  • gallde - Thursday, June 11, 2009 - link

    You point out that TRIM will only work on deletions, not on overwrites. But, couldn't a smart controller look at blocks that have a majority of invalid pages and "trim" them as well, recovering clean pages as a background process? Reply
  • forsunny - Thursday, August 13, 2009 - link

    Why not just make the SSDs capable of individual page erases instead of blocks? Problem solved. Reply
  • Ron White - Sunday, August 31, 2014 - link

    Erasing the NAND transistor in an SSD requires such a large jolt of voltage that it would affect surrounding transistors. Reply
  • lyeoh - Friday, May 29, 2009 - link

    Good and informative article.

    Regarding the shill tshen83 who claims that Anandtech cost the drive manufacturers millions of dollars in sales.

    If that is true, Anandtech has saved customers millions of dollars.

    Anandtech should care more about their readers losses than drive manufacturer losses. If Anandtech was a site for drive manufacturers and their shills we wouldn't be reading it.

    To me, if the SSD drive manufacturers lose money, it's their own fault for building crap that has higher write latencies than old fashioned drives with metal discs spinning at 7200RPM or slower. Not anandtech's.

    I can get higher sequential reads and writes by using RAID on old fashioned drives. It is much harder to get lower latency. So Anandtech did the right thing for OCZ.

    Lastly, there might be a way of making your windows machine stutter less even with a crap SSD. Note: I haven't tested the actual effect on an SSD because I don't have an SSD.

    Basically by default when Windows accesses a file on NTFS, it will WRITE to the directory the time of the access. Yep, it writes when it opens files and directories (which are just special files). That might explain the stuttering people see. For a lot of things, Windows has to open files.

    Warning! There are reasons why some people or programs would want to know the last access time of files. Me and my programs don't (and I doubt most people would).

    If you are sure that's true for you (or are willing to take the risk) set NtfsDisableLastAccessUpdate=1 as per:

    http://technet.microsoft.com/en-us/library/cc75856...">http://technet.microsoft.com/en-us/library/cc75856...
    Reply
  • poohbear - Sunday, April 26, 2009 - link

    Brilliant article and very informative on these emerging technology. I wont be buying one anytime soon @ their prices, but good to know we'll FINALLY be replacing convential HDD which are the one component that have been pretty much the same since as far back as i can remember

    "SSDs have +5 armor immunity to random access latency"

    rofl that's the best analogy i've seen on a hardware review site. is every comp geek a RPG geek @ heart?
    Reply
  • Gootch - Sunday, April 19, 2009 - link

    Great article. Realy made me understand what I need to look at before making the plunge. Mistakes and all, my compliments. As for value between the now seemingly drastically improved Vertex vs the X25-M, I compared prices between the two and per Gb, the Intell product for say an 80 Gb drive is Can $5.86/Gb, while the OCZ 60 Gb SSD is Can $6.81/Gb. Now that we are no longer comparing apples and oranges, I think we need to point out that the Intel product is not only faster and maintains it's performance edge better, but it is cheaper per Gb. At least in Canada. I have many OCZ products and I love the company and it's customer support. I can only hope that they will make their SSDs more competitive in the near future, because most consumers will pay the extra 70 bucks and go with the X25 when they pay attention to the numbers, both performance and price. Reply

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