Performance Over Time & TRIM

SandForce has always exhibited strange behavior when it came to TRIM. Even Intel's custom firmware in the SSD 520 wasn't able to fix SandForce's TRIM problem. The issue happens when the SSD is completely filled with incompressible data (both user LBAs and spare area). Any performance degradation after that point won't be restored with a TRIM pass and instead will require a secure erase to return to new. I didn't expect the 335 to fix this but I still tortured the SSD 335 for 60 minutes, ran AS-SSD, TRIMed and reran AS-SSD:

Intel SSD 335 - Resiliency - AS SSD Sequential Write Speed - 6Gbps
  Clean After Torture (60min) After TRIM
Intel SSD 335 240GB 317.7MB/s 174.2MB/s 176.9MB/s

And the issues persists. This is really a big problem with SandForce drives if you're going to store lots of incompressible data (such as MP3s, H.264 videos and other highly compressed formats) because sequential speeds may suffer even more in the long run. As an OS drive the SSD 335 will do just fine since it won't be full of incompressible data, but I would recommend buying something non-SandForce if the main use will be storage of incompressible data.

AnandTech Storage Bench 2011 - Light Workload Power Consumption
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  • Per Hansson - Tuesday, October 30, 2012 - link

    No, it does not work like that.
    A slow DMM might take a reading every second.
    An example, in seconds:
    1: 2w
    2: 2w
    3: 2w
    Average=2w

    A fast DMM might take readings every 100ms:
    1: 2w
    2: 0.5w
    3: 2w
    4: 0.5w
    Average=1w

    As you see a DMM does not take a continous reading, it takes readings at points in time and averages those...

    An SSD drive might actually change power levels much more frequently, like every millisencond (consider their performance, how long does it take to write 4KB of data as an example?)
    Reply
  • hrga - Thursday, November 1, 2012 - link

    dont think SSD even try to write such a small amount of data as 4kB every milisecond considering how large buffers usually have 128GB LPDDR2. So thes kind of small writes occur in bursts when they accumulate every 15-30s (at least hope so as this was case with hard drives) That ofc depends on firmware and values in it. Reply
  • Per Hansson - Thursday, November 1, 2012 - link

    That makes no difference, I sincerely hope that no drive waits 15 > 30 seconds to write data to disk because that is just a recipe for data loss in case of power failure or BSOD.
    I also hope no drive uses a 128GB write cache. (Intel's in house controller keeps no user data in cache as an example, but I digress)

    Even if the drive waits a minute before it writes the 4KB of data you must still have a DMM capable of catching that write, which is completed in less than a millisecond.
    Otherwise the increased power consumption during the disk write will be completely missed by the DMM
    Reply
  • Mr Alpha - Monday, October 29, 2012 - link

    Wouldn't it make more sense to the idle power consumption on a platform that supports DPIM? The idle power usage is mostly a matter on mobile devices, and it is on those you get DPIM support. Reply
  • sheh - Monday, October 29, 2012 - link

    The text says total writes were 1.2TB, (+3.8TB=) 5TB, and 37.8TB. The screenshots show "host writes" at 1.51TB, 2.11TB, and 3.90TB? Reply
  • sheh - Monday, October 29, 2012 - link

    And why the odd power on hours counts? Reply
  • Kristian Vättö - Monday, October 29, 2012 - link

    You are mixing host writes with the actual NAND writes. Host writes are the data that the host (e.g. an operating system) sends to the SSD controller to write. NAND writes show much is written to the NAND.

    When the SSD is pushed to a corner like I did, you will end up having more NAND writes than host writes because of read-modify-write (i.e. all user-accessible LBAs are already full, so the controller must read the block to a cache, modify the data and rewrite the block). Basically, your host may be telling the controller to write 4KB but the controller ends up writing 2048MB (that's the block size).
    Reply
  • extide - Monday, October 29, 2012 - link

    Block size is 2048KB* Reply
  • sheh - Monday, October 29, 2012 - link

    So the write amplification in the end was x9.7?

    Are NAND writes also reported by SMART?

    And with the messed up power on count, how can you know the rest of the SMART data is reliable?
    Reply
  • Kristian Vättö - Tuesday, October 30, 2012 - link

    Yes, write amplification was around 9.7x in the end. That makes sense because the drive becomes more and more fragmented the more you write to it.

    As you can see in the screenshots, the SMAT value F9 corresponds to NAND writes. Most manufacturers don't report this data, though.

    We just have to assume that the values are correct. Otherwise we could doubt every single test result we get, which would make reviewing impossible. The data makes sense so at least it's not screaming that something is off, and from what I have read, we aren't the only site who noticed weird endurance behavior.
    Reply

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