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I have a Windows 7 Pro HP z200 system with an MTFDBAK256MAG-1G1 (Micron RealSSD C300 240 GB). I notice that the drive's performance is fine when the disk is booted, then during the course of a Windows session the read performance drops to 1/10 of it was at the start!

And, rebooting returns the SSD to its original speed. In/out of sleep mode does not have the same effect. I've tried all the standard tweaks after installing the SSD into a computer (Registry settings, superfetch disabled, etc.).

The disk is about three years old; I actually had it in my laptop but moved it to this desktop, replacing a SATA HDD. Is this a characteristic of an SSD getting old? Are there diagnostic utilities that can tell if there is something going wrong with the disk? I have Intel Rapid Storage Technology installed and it says everything is fine, as does sfc and chkdsk.

Below are some specific data points that may further explain what I'm seeing. I don't have any tests that could be replicated here; perhaps someone knows of a continuous output read tester?


One way I can tell is, I have a script which I call from a command line. It allows me to do regex searches on a recursive/ wildcard set of text files; a small perl script is called for each file that does the regex search. I have a little status indicator that increments a counter for each file processed.

In a directory with 200 text files, none over 70kB, the script starts processing about 20 files/sec. After about 50 files, the speed visibly drops until near the end of the processing, the script is processing TWO files/sec. Worse, once this happens, running the script over the same set of files with the same criterion, or over any set of files with different criterion, the performance is now the same!

I know it's not just the script, because once this happens, starting a new program, or closing an existing program, takes several seconds.

Final data points: on my colleague's machine, which has a Kingston SV300 100 GB SSD drive, the same script over the same 200 files with the same criterion never wavers from the ~20 files/sec benchmark. This can be repeated many many times with no slowdown. And the consistent rate on my laptop with its old SATA HDD is 10 files/sec.

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    Why do you attribute this performance loss to the SSD rather than to, say, the CPU? Jan 21, 2015 at 4:19
  • Hmm, what makes you ask about the CPU & not the drive?
    – cniggeler
    Jan 21, 2015 at 4:47
  • do you use the latest Firmware for the SSD? Jan 21, 2015 at 5:53
  • Yes, it's at the latest. And BTW it ran consistently when it was in the laptop.
    – cniggeler
    Jan 21, 2015 at 10:06
  • Would it help to somehow erase or reformat? I can back it up, erase, and try again...
    – cniggeler
    Jan 21, 2015 at 10:15

3 Answers 3

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It was the different antivirus software I installed - Webroot SecureAnywhere.

After making no progress exiting Chrome and stopping processes I didn't have on the other machines (print/scan utilities, a "USB3 monitor", and so forth), there was no difference in performance. The only other thing was Webroot; I've used AVG and Ad-Aware in the past.

When I turned off Webroot completely, the issue went away. Working my way into Webroot's various functions, I changed permissions for the script (and its perl call inside it) from Monitor to Allow in PC Security - Allow/Block Files.

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Several possibilities:

  1. You have less than 20% free space on the disk. SSD technology (and TRIM especially) rely on some amount of free space to move data around (and I mean physically, not the free space on logical drive).
  2. Your SSD is a bit old and was used in older systems (SATA 3GB/s, with which HP z200 is equipped, does not support queued TRIM), so most of TRIM functionality is the drive build-in part. So it got used up considerably.
  3. There are some applications which can visibly degrade ssd performance during session (for example, Chrome Browser comes to mind) with heavy swapping.
  4. Some types of data (generally speaking: uncompressible) can lower performance on SSDs
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I had a similar problem with my OCZ Vertex 4..

The solution is a special type of defragmentation called "Free space consolidation".

The need for this arises because TRIM only works on blocks that are completely empty.. In other words if your block size is 4KB and your files on average only use 1KB of that block, your disk might show 60% free space and yet when trim executes.. only a small amount of blocks are freed up for usage.

Your system slows down then because there is a bottleneck of processes looking for free contiguous disk space to use (primarily for caching purposes).

These blocks are quickly used after a few minutes of using your computer..

Raxco's Perfect Disk software also has a very light version of this made specifically for SSD use called "SSD Optimize".

Although I personally fixed my Vertex 4 with the full "Free Space Consolidation" defrag pass.

You can download a free trial.

You can also look for a free solution, though I don't know of any off hand that for certain have that feature.

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