I have a freshly installed and updated version of Windows Server 2016, I have 4x 4TB disks, connected through SATA. These disks are setup in a parity configuration under a StoragePool, in that I have made a virtual disk of ~10TB.

Write operations to the disk go around 10MB/s after the RAM buffer has filled, an ideas why?



  • Iperf3 - Network connection is working correctly.
  • CPU Load - 10% or lower.
  • Hardware Failure - Disk drives are functional and controller works fine on individual disks.


The Storage Pool's Write Pattern Link

iPerf3 Results Link

Write Pattern During LOCAL C: to O: Transfer (No Networking): Link

Requested Info:

  • Disk RPM/Size: 7200RPM (LFF)
  • Disk Models: WD40EFRX (Western Digital: Red "NAS" Drives)
  • Storage Pool Setup: See Here
  • What kind of server? Custom-Chassis PC Case with a "Asus P8Z77-V LE Plus" Motherboard.
  • How are disks connected to it? 12 Disks, 4 of which are relevant to this file share.

Additional Notes - The system was performing in the range of 200MB/s previosuly with FreeNAS 11.4.

  • Please add more information: Disk RPM and size (SFF or LFF) and your Storage Pool setup Dec 28, 2018 at 21:41
  • It looks like you are falling back to the performance of one disk and less... SATA is not the best for performance and without a real RAID with cache and battery all writes will be slow (sync) to ensure data safety... Dec 28, 2018 at 21:52
  • It's likely not 7200 - but 5400rpm. And you can find some tests here: storagereview.com/wd_red_4tb_hdd_review_wd40efrx Dec 28, 2018 at 22:02
  • What kind of server? How are disks connected to it? Check write IO without RAID on each disc.
    – shallrise
    Dec 28, 2018 at 22:04
  • You're right it is 5400RPM, sorry. I Agree that a RAID controller would be a great addition however the current speeds of 10MB/s are far lower than expected even out of SATA, do you agree?
    – ISJ
    Dec 28, 2018 at 22:05

2 Answers 2


The default settings will not fit.

Optimizing Storage Spaces (recommended way)

Setting the interleave should be done without GUI with PowerShell: New-VirtualDisk -Interleave

I would not recommend to change the IsPowerProteced settings or enable write cache on the physical disks.


The loss of performance you are experiencing is probably caused by the fact that Windows has to compute the partiy, and because the storage pool is probably using "write-through" (waiting for the blocks to be successfully written to the disk).

You can disable write-through and disable the flush operations by using the Set-StoragePool command with the -IsPowerProtected switch.

More information about this optional parameter on the documentation: https://docs.microsoft.com/en-us/powershell/module/storage/set-storagepool?view=win10-ps#optional-parameters

However, don't do that if your server IS NOT power protected. If you aren't using a power-protected disk controller, and if you aren't using an UPS to power-protect your server, don't use the PowerProtected mode in your production environment. In case of a power failure, or if Windows is stopped unexpectedly, will most likely lead to loss of data.

However, you can still do it for testing purposes to see if the throughput is better.

  • This boosted the performance from 8.9MB/s to 18.2MB/s, so good call, however this is still far below the expected values. Any other ideas on detecting bottlenecks? What about block sizes?
    – ISJ
    Dec 28, 2018 at 22:46
  • I don't think this is far below the expected values since you are using parity. Microsoft reached ~25MB/s "The caveat of a parity space is low write performance compared to that of a simple or mirrored storage space, since existing data and parity information must be read and processed before a new write can occur." source
    – Swisstone
    Dec 28, 2018 at 23:06
  • block sizes can be important - but this is more a filesystem point of view. The blocksize will be defined when you're formatting the StoragePool with your desired filesystem type. Dec 28, 2018 at 23:07

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