We've started to deploy SSD drives to our developers workstations. At this moment we're having the unpleasant surprise that the systems using the new SSDs often freeze, with the HDD activity led blinking or being continuously on. Benchmarks shows read speeds around 180 MB/s, but write speeds around 5 MB/s. All developers are using Windows 7 Enterprise, 64 bit, SP1. The SSDs are Kingston SV200S3128G. One of our developers suggested (based on his experience) the following sequence:

  • backup the workstation
  • use a tool to completely erase the SSD
  • make sure AHCI is enabled in BIOS
  • install Windows
  • restore from backup

So far, this procedure seems to work (we're still testing, but write speed seems to be 120 MB/s). There are some questions in this context:

  • why do we have to completely reinstall Windows?
  • Is it possible to clean the SSD without reinstalling Windows? Is there a reliable tool?
  • If AHCI was disabled when Windows was installed and we enable it, shouldn't this be enough to correct the write performance issue?
  • If we have to completely erase the SSDs, does this mean the SSDs we've received were used before (SH)? I'm wondering this because the package I've got was open (I didn't think about it at that time, as I considered one of my coworkers simply took a peek inside the package).
  • Has anyone seen a similar problem before?
  • 3
    What brand and model are the SSDs? I've found huge discrepancies in performance between low, mid, and high end drives.
    – EEAA
    Mar 30 '12 at 0:01
  • They are Kingston (I'll lookup their model in the morning, when I'll be in the office). However, as I've said, it seems the performance is ok once we erase them and reinstall Windows with AHCI enabled upfront. This is what puzzles me.
    – Dan
    Mar 30 '12 at 0:04
  • 1
    Have you looked into TRIM? It's supposed to improve performance in the long term, where prolonged use would cause slowdowns such as what you are seeing: en.wikipedia.org/wiki/TRIM The filesystem needs to support it though. In linux you can, for example, mount the ext4 filesystem with the discard option which turns on TRIM.
    – aseq
    Mar 30 '12 at 0:22
  • @aseq: we're using W7, which supports TRIM OOB. Again, I would have expected that issuing TRIM and enabling AHCI post-install will fix the performance issue. I want to avoid reinstalling Windows, if possible (it also looks an odd operation).
    – Dan
    Mar 30 '12 at 0:44
  • @ErikA: the SSD is Kingston SV200S3128G.
    – Dan
    Mar 30 '12 at 12:10

There are 3 things that come to mind. Firstly, what brand / model SSD are you using?? There have been some problems recently with controllers from certain manufactures. Secondly, Is TRIM enabled. Win7 will enable TIRM (if required) at installation time. So if the SSD was not present then, it may not be enabled. To check:

In an Elevated command Prompt windows, type the following:

fsutil behavior query disabledeletenotify
Results explained below:
DisableDeleteNotify = 1 (Windows TRIM commands are disabled)
DisableDeleteNotify = 0 (Windows TRIM commands are enabled)

Thirdly, Does the SSD have the correct sector alignment. To check the alignment of your SSD's partition:

In Windows, run msinfo32
click on: components -> storage -> disks

Look for your SSD and check the partition starting offset.

It needs to be divisible by 4096 otherwise the alignment is not correct.

  • The model is Kingston SV200S3128G. I've edited the question, so other people will see it upfront. TRIM is enabled and the partition is correctly aligned.
    – Dan
    Mar 30 '12 at 12:05

If it happened after some time - it can be a TRIM support problem at your side. If it worked like that from the beginning - the drives may be used. If system does not support TRIM command, drive does not know, where free blocks and where used blocks. So, once drive is filled, drive controller should erase big block of data, store untouched blocks, merge data from the actual write and stored blocks and then write, this is why it's so slow. Erase block is 128k and write block is 4k(8k) usually. Intel have special utility that can do the work of TRIM command, but looks like Kingston have no such utility. So, reinstall is the better way.


Modern desktop harddrives have two modes: 1) Emulate ancient ATA drives 2) Modern SATA with Tagged commands/AHCI. These two use different ways for controlling the drive.

If your windows was installed without AHCI enabled then windows would have detected drives as ATA disks and it will have selected the right driver for that.

If your windows was installed with AHCI enabled then windows would have detected drives modern drives and it will load a different driver.

If you put your windows boot drive on this disk and you change their mode then windows will try to start with the wrong driver. It will not find c: (aka $bootdrive) and it will fail to boot.

For this reason a reinstall might be easiest..

  • It's easy to instruct Windows 7 to use AHCI instead of ATA. See ithinkdiff.com/…. Reinstalling Windows is by no means an easy way.
    – Dan
    Mar 30 '12 at 12:01

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