Storage Space Random Write Performance Drop

[nideii]

Long story shorten ahead: when writing large amount of data, there is a significant performance drop every 10 seconds.

 

I admit I am using a very wire setup for my raid. I have a Intel 4960X with 16GB of RAM, and some very old HDD with different capacity and some old SSDs.

I will prefer to use Windows, since I already have some external drives laying around using NTFS and almost full. Thus, the OS of my NAS is Windows 10 Workstation Pro.

 

I setup a Storage Space Pool with two same capacity (both are 512GB) SSD as SSD tier, and around 8 different capacity SATA HDD. 

 

Here is the powershell script I used to create a such thing.

```

Get-StoragePool -FriendlyName $StoragePoolName `
    | Get-PhysicalDisk `
    | ? MediaType -eq SSD `
    | Set-PhysicalDisk -Usage Journal

$SSDTier = New-StorageTier -StoragePoolFriendlyName $StoragePoolName -FriendlyName $SSDTierName -MediaType SSD -ResiliencySettingName "Mirror"
$HDDTier = New-StorageTier -StoragePoolFriendlyName $StoragePoolName -FriendlyName $HDDTierName -MediaType HDD -ResiliencySettingName "Parity"

 

New-VirtualDisk -StoragePoolFriendlyName $StoragePoolName `
-FriendlyName  $SpaceName`
-ResiliencySettingName "Parity" `
-WriteCacheSize 384GB `
-UseMaximumSize -AutoNumberOfColumns `

```

Per MSDN doc, this should use SSD as mirror for faster tier. I used HWINFO64 to check the ssd usage, and two SSDs both have the same load across them when writing to the pool.

 

I did have some very good read performance, and I could have around 300MiB/s for small amount of data writing to the Storage Space. But writing more than 10G at one time, could have performance drop to 30MiB/s and be back a few seconds.

I tried to lower the `WriteCacheSize` to around 1G (which should be the default value), and it make it worse, much lower number overall (~120MiB/s).

[leadeater]

Can you point me to the Microsoft documentation you followed? Looks to me you have mixed different configurations together, you have created some Storage Tiers but not actually used them when you created the virtual disk and if you want to use Storage Tiers to create a Multi-Resilient Virtual Disk you don't set the SSD usage to Journal.

 

You either use just Storage Tiers, which technically isn't supported in a single system configuration btw, or you add SSDs to the pool and set them to Journal mode and they will act as a Write-Back Cache.