In this blog post we will continue our step by step series on Microsoft Storage Spaces, if you missed the previous post on How To Replace A Faulty Disk In Two-Way Mirrored Storage Tiered Space, then make sure you check it here.
In today’s post I will walkthrough how to create a Two-way mirror Storage Space via PowerShell.
So without further ado, let’s get started.
First we will check the available physical disks in the system:
PS C:\>Get-PhysicalDisk
Next we will list the physical disks that can be pooled into our Storage Pool filtered by Friendly Name, Operation Status, Size and Media Type.
PS C:\>Get-PhysicalDisk –CanPool $True | ft FriendlyName,OperationalStatus,Size,MediaType
As you can see we have 4 disks that can be pooled (2X136GB and 2X418GB).
We will store all physical disks that can be pooled into a variable, $Pooldisks
PS C:\>$Pooldisks = Get-Physicaldisk | ? {$_.canpool -eq $true}
Next we will create a new Storage Pool using the disks in variable $Pooldisks with a name of “DCHV-StoragePool1”
PS C:\>New-StoragePool -PhysicalDisks $Pooldisks –StorageSubSystemFriendlyName “Storage Spaces*” -FriendlyName “DCHV-StoragePool1”
Here is the result in the UI:
Now let’s view the disks in the Storage Pool that we just created.
PS C:\>Get-StoragePool -FriendlyName “DCHV-StoragePool1” | Get-PhysicalDisk | Select FriendlyName, MediaType
As you can see the MediaType is shown as UnSpecified, so before we continue we must set the MediaType properly.
And since I am using only Normal Hard Drives in this demonstration, we will set the MediaType to HDD, and if you are creating a tiered Storage Space, then make sure to set each type properly (HDD / SSD).
PS C:\>Get-StoragePool DCHV-StoragePool1 | Get-PhysicalDisk | Set-PhysicalDisk -MediaType HDD
Let’s view the disks in the Storage Pool after we specified the media type to HDD:
PS C:\>Get-StoragePool -FriendlyName “DCHV-StoragePool1” | Get-PhysicalDisk | Select FriendlyName, MediaType
Last but not least, we will create a New-VirtualDisk with ResiliencySettingName Mirror, then the NumberOfDataCopies is equal to (2=Two-way mirror Space, 3=Three-way mirror Space). In this demo we can only create Two-way mirror space since we have only 4 disks, however for Three-way mirror we need 5 disks. A two-way mirror will allow you to suffer the loss of a single disk with no problems while a three-way mirror will allow you to lose two disks.
Next we move to choose the ProvisioningType (Fixed or Thin), we will choose Fixed instead of Thin provisioning, and then we specify Maximum disk size. It’s very important to mention that thin provisioning will not prevent storage shortages. Applications will break if storage is not added to the thinly provisioned volumes in time.
The final and confused parameters are the NumberOfColumns and the Interleave.
The more columns means more performance because multiple disks will be engaged at once in Read/Write operations, but it’s also limited in flexibility with expanding existing virtual disks, especially in tiered scenarios. So what’s the best size for columns for Two-way mirror Storage Space?
Typically the column count will be equal to the number of physical disks of the storage space (for simple spaces) or half of the number of disks (for mirror spaces). The column count can be lower than the number of physical disks but never higher.
The more is better in terms of performance, but the less is better in terms of flexibility for future expansion. There is no simple answer here, so it depends!
Here is a Two-way mirror virtual disk with Number of Columns=1.
PS C:\>New-VirtualDisk -StoragePoolFriendlyName DCHV-StoragePool1 -FriendlyName DCHV01-vDisk1 -ResiliencySettingName Mirror -NumberOfDataCopies 2 -ProvisioningType Fixed -UseMaximumSize -NumberOfColumns 1 -Verbose
Here is a Two-way mirror virtual disk with Number of Columns=2.
PS C:\>New-VirtualDisk -StoragePoolFriendlyName DCHV-StoragePool1 -FriendlyName DCHV01-vDisk1 -ResiliencySettingName Mirror -NumberOfDataCopies 2 -ProvisioningType Fixed -UseMaximumSize -NumberOfColumns 2 -Verbose
As you can see with Column#1, we have more capacity space than Column#2. If you use 1 column, your space will only be as fast as one individual disk.
The Interleave parameter represents the amount of data written to a single column per stripe. The default Interleave value is 262,144 bytes (256 KB).
The final step is to initialize the volume and create the new partition.
PS C:\>Get-VirtualDisk DCHV01-vDisk1 | Get-Disk | Set-Disk -IsReadOnly 0
PS C:\>Get-VirtualDisk DCHV01-vDisk1 | Get-Disk | Set-Disk -IsOffline 0
PS C:\>Get-VirtualDisk DCHV01-vDisk1 | Get-Disk | Initialize-Disk -PartitionStyle GPT
PS C:\>Get-VirtualDisk DCHV01-vDisk1 | Get-Disk | New-Partition -DriveLetter “D” -UseMaximumSize
PS C:\>Initialize-Volume -DriveLetter “D” -FileSystem NTFS -Confirm:$false -NewFileSystemLabel “Hyper-V”
Microsoft has a great Storage Space performance paper which goes in more detail and is worth a read.
Until then… N’joy your day!
/Charbel
