Get-StorageTierSupportedSize result is invalid

[i3v]

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Links

• https://learn.microsoft.com/en-us/powershell/module/storage/get-storagetiersupportedsize?view=windowsserver2019-ps

Summary

The TierSizeMax property of the Get-StorageTierSupportedSize result is not explicitly defined and counterintuitive. AFAIU, it is also not calculated correctly. I think that this is a major bug in a critical subsystem and thus it should be fixed ASAP.

The example below demonstrates that although TierSizeMax is 6725 GB (while the AllocatedSize is 1777.5GB), but I can actually resize this tier to 12937.5 GB. Thus, TierSizeMax is neither "how large my pre-existing tier could become", nor "how large a new, additional tier could be".

Details

Here's the full example:

$StoragePoolName = "DataStorePool1"
$VDiskName = "DataStoreVDisk1"
$ResiliencySetting = "Simple"
$SSDTierName = "SSDTier"
$HDDTierName = "HDDTier"

#List all disks that can be pooled and output in table format (format-table)
Get-PhysicalDisk -CanPool $True | ft FriendlyName,OperationalStatus,Size,MediaType,SerialNumber

#Store all physical disks that can be pooled into a variable, $PhysicalDisks
$PhysicalDisks = (Get-PhysicalDisk -CanPool $True | Where FriendlyName -NE "ATA Samsung SSD 870")
$PhysicalDisks

#  Number FriendlyName         SerialNumber                             MediaType CanPool OperationalStatus HealthStatus Usage           Size
#  ------ ------------         ------------                             --------- ------- ----------------- ------------ -----           ----
#  9      NVMe Samsung SSD 970 0025_385A_01B2_1E04.                     SSD       True    OK                Healthy      Auto-Select  1.82 TB
#  0      ATA WDC WD181KRYZ-01 3WGN974J                                 HDD       True    OK                Healthy      Auto-Select 16.37 TB
#  10     NVMe Samsung SSD 970 0025_385A_01B2_1E13.                     SSD       True    OK                Healthy      Auto-Select  1.82 TB
#  6      XPG GAMMIX S70 BLADE 0000_0000_0000_0000_707C_18E8_B47D_B752. SSD       True    OK                Healthy      Auto-Select  7.28 TB
#  8      NVMe Samsung SSD 970 0025_385A_01B2_1E02.                     SSD       True    OK                Healthy      Auto-Select  1.82 TB
#  5      ATA WUH721818ALE6L4  6RG9Z5RW                                 HDD       True    OK                Healthy      Auto-Select 16.37 TB
#  1      ATA WDC WD181KRYZ-01 3WJKB5LK                                 HDD       True    OK                Healthy      Auto-Select 16.37 TB
#  4      ATA WUH721818ALE6L4  6RG9Z5UW                                 HDD       True    OK                Healthy      Auto-Select 16.37 TB

$PD_set1 = $PhysicalDisks | Where-Object { $_.SerialNumber -like "0025_385A_01B2_1E04*" -or $_.FriendlyName -like "*WD181KRYZ*"}

#Create a new Storage Pool using the disks in variable $PD_set1, to ensure appropriate number of columns
$SubSysName = (Get-StorageSubSystem).FriendlyName
New-StoragePool -PhysicalDisks $PD_set1 -StorageSubSystemFriendlyName $SubSysName -FriendlyName $StoragePoolName

#View the disks in the Storage Pool just created
Get-StoragePool -FriendlyName $StoragePoolName | Get-PhysicalDisk | Select FriendlyName, MediaType

#Create two tiers in the Storage Pool created. One for SSD disks and one for HDD disks
$SSDTier = New-StorageTier -StoragePoolFriendlyName $StoragePoolName -FriendlyName $SSDTierName -MediaType SSD -NumberOfColumns 1 -ResiliencySettingName $ResiliencySetting  # default interleave 

$HDDTier = New-StorageTier -StoragePoolFriendlyName $StoragePoolName -FriendlyName $HDDTierName -MediaType HDD -NumberOfColumns 2 -ResiliencySettingName $ResiliencySetting  # default interleave 

#Identify tier sizes within this storage pool
$SSDTierSizes = (Get-StorageTierSupportedSize -FriendlyName $SSDTierName -ResiliencySettingName $ResiliencySetting).TierSizeMax
$HDDTierSizes = (Get-StorageTierSupportedSize -FriendlyName $HDDTierName -ResiliencySettingName $ResiliencySetting).TierSizeMax

#Create a new virtual disk in the pool with a name of TieredSpace using the SSD and HDD tiers -----------------------------------------------

       
# case_20 (NTFS - formatted, 32K cluster size), final
$WbcSize  = 32GB
$ssd_usable = $SSDTierSizes - ($WbcSize * 2) - 20GB
$hdd_usable = $HDDTierSizes - 100GB
New-VirtualDisk -StoragePoolFriendlyName $StoragePoolName -FriendlyName $VDiskName -StorageTiers $SSDTier, $HDDTier -StorageTierSizes @($ssd_usable, $hdd_usable) -ResiliencySettingName $ResiliencySetting  -WriteCacheSize ($WbcSize) -ProvisioningType Fixed -NumberOfDataCopies 1 -Interleave 256KB

 
 
# check actual number of columns:
Get-VirtualDisk -FriendlyName "DataStoreVDisk1" | Get-StorageTier | Select FriendlyName, NumberOfColumns, ResiliencySettingName
#
# FriendlyName            NumberOfColumns ResiliencySettingName
# ------------            --------------- ---------------------
# DataStoreVDisk1-SSDTier               1 Simple
# DataStoreVDisk1-HDDTier               2 Simple


# add other disks
$PhysicalDisks = (Get-PhysicalDisk -CanPool $True | Where FriendlyName -NE "ATA Samsung SSD 870")
Add-PhysicalDisk -PhysicalDisks $PhysicalDisks -StoragePoolFriendlyName $StoragePoolName

Get-VirtualDisk -FriendlyName $VDiskName | Get-StorageTier
# 
# FriendlyName            TierClass   MediaType ResiliencySettingName FaultDomainRedundancy     Size FootprintOnPool StorageEfficiency
# ------------            ---------   --------- --------------------- ---------------------     ---- --------------- -----------------
# DataStoreVDisk1-SSDTier Performance SSD       Simple                0                      1.75 TB         1.75 TB           100.00%
# DataStoreVDisk1-HDDTier Capacity    HDD       Simple                0                     32.73 TB        32.73 TB           100.00%

# ======================================= Optimize =====================================================================

Optimize-StoragePool -FriendlyName $StoragePoolName
Get-StorageJob
# Name                         IsBackgroundTask ElapsedTime JobState PercentComplete BytesProcessed BytesTotal
# ----                         ---------------- ----------- -------- --------------- -------------- ----------
# DataStorePool1-Optimize      False            1.11:31:12  Running  97                    35.75 TB   36.72 TB
# DataStorePool1-Optimize      False            1.11:31:12  Running  97                    35.75 TB   36.72 TB
# DataStoreVDisk1-Regeneration True             00:00:10    Running  50                     4.06 GB       8 GB

Get-StorageTier | Select-Object FriendlyName, @{L='Size(GB)';E={$_.Size/1GB}}, @{L='AllocatedSize(GB)';E={$_.AllocatedSize/1GB}}
# FriendlyName            Size(GB) AllocatedSize(GB)
# ------------            -------- -----------------
# DataStoreVDisk1-SSDTier   1777.5            1777.5
# SSDTier                        0                 0
# DataStoreVDisk1-HDDTier    33426             33426
# HDDTier                        0                 0
#
# I've got no idea why it creates two new tiers, instead of using those I've explicitly provided...

Remove-StorageTier -FriendlyName $SSDTierName
Remove-StorageTier -FriendlyName $HDDTierName

Get-StorageTier | Select-Object FriendlyName, @{L='Size(GB)';E={$_.Size/1GB}}, @{L='AllocatedSize(GB)';E={$_.AllocatedSize/1GB}}
# FriendlyName            Size(GB) AllocatedSize(GB)
# ------------            -------- -----------------
# DataStoreVDisk1-SSDTier   1777.5            1777.5
# DataStoreVDisk1-HDDTier    33426             33426

$VD_SSDTierName = $VDiskName + "-" + "SSDTier"
$VD_HDDTierName = $VDiskName + "-" + "HDDTier"

$VD_SSDTier = Get-StorageTier -FriendlyName $VD_SSDTierName
$VD_HDDTier = Get-StorageTier -FriendlyName $VD_HDDTierName

$VD_SSDTierSize_buggy_max = (Get-StorageTierSupportedSize -FriendlyName $VD_SSDTierName -ResiliencySettingName $ResiliencySetting).TierSizeMax
$VD_HDDTierSize_buggy_max = (Get-StorageTierSupportedSize -FriendlyName $VD_HDDTierName -ResiliencySettingName $ResiliencySetting).TierSizeMax

$VD_SSDTierSize_buggy_max / 1GB
6725
# Bullshit, severely underestimated.

$VD_HDDTierSize_buggy_max / 1GB
33624
# This might be correct, if this is "how much can we add"

$VD_SSDTierSize_true_max = (Get-StoragePool -FriendlyName $StoragePoolName | Get-PhysicalDisk | Where-Object {$_.MediaType -eq 'SSD'} | Measure-Object -Property Size -Sum).Sum - ($WbcSize * 2) - 40GB
$VD_HDDTierSize_true_max = (Get-StoragePool -FriendlyName $StoragePoolName | Get-PhysicalDisk | Where-Object {$_.MediaType -eq 'HDD'} | Measure-Object -Property Size -Sum).Sum - 100GB

$VD_SSDTierSize_true_max / 1TB
# 12.633873552084

$VD_HDDTierSize_true_max / 1TB
# 65.38671875

# ======================================= Resize VD ====================================================================

Resize-StorageTier -FriendlyName $VD_SSDTierName -Size  $VD_SSDTierSize_true_max
Resize-StorageTier -FriendlyName $VD_HDDTierName -Size  $VD_HDDTierSize_true_max

Get-StorageTier | Select-Object FriendlyName, @{L='Size(GB)';E={$_.Size/1GB}}, @{L='AllocatedSize(GB)';E={$_.AllocatedSize/1GB}}
# FriendlyName            Size(GB) AllocatedSize(GB)
# ------------            -------- -----------------
# DataStoreVDisk1-SSDTier  12937.5           12937.5
# DataStoreVDisk1-HDDTier    66956             66956

(Get-VirtualDisk -FriendlyName "DataStoreVDisk1").Size / 1GB
79893.5

# speedcrunch: (2+2+2+8+18*4)*1e12/2^(30) = 80093.74141693115234375

# ======================================= Format VD ====================================================================

Get-VirtualDisk -FriendlyName $VDiskName | Get-Disk | Initialize-Disk -PartitionStyle GPT

$Partition = Get-VirtualDisk -FriendlyName $VDiskName | Get-Disk | New-Partition -UseMaximumSize -DriveLetter H

Format-Volume -Partition $Partition -FileSystem NTFS -AllocationUnitSize 64KB -NewFileSystemLabel "HData"
# DriveLetter FriendlyName FileSystemType DriveType HealthStatus OperationalStatus SizeRemaining     Size
# ----------- ------------ -------------- --------- ------------ ----------------- -------------     ----
# H           HData        NTFS           Fixed     Healthy      OK                     78.02 TB 78.02 TB

Suggested Fix

1. Please explicitly define the intended meaning of the TierSizeMax in the docs

   • Is it "how large my pre-existing tier could become" or "how large a new, additional tier could be" or "just a mild suggestion about either"?

2. Please document down the arithmetic behind this.

   • Is it correct, that I should subtract the $WbcSize * 2 (based on my old experiments, it looks like Write-Back cache footprint is twice it's size (i.e. it's probably always a 2-way mirror, despite this is not documented anywhere)
   • Please document down if I need to subtract a few more GB for the various metadata (how much?)
   • Please document down if I need to leave some "unallocated space" for the tier-optimization to work adequately.
   • Please document down how is the TierSizeMax related to the The capacity consumption of the storage pool {some-id} has exceeded the threshold limit set on the pool. Return Code: STATUS_SUCCESS message in the "StorageSpaces-Driver" event log. Especially, for the Fixed provisioning (tiered storage spaces).

3. Please review the actual code behind the Get-StorageTierSupportedSize and fix it. Make it provide more adequate values. I guess that he VD_SSDTierSize_true_max and the VD_HDDTierSize_true_max in my example script are actually a better estimates.