Redistribute Mailboxes Across an Exchange 2010 DAG

I have put together a script to redistribute mailboxes across an Exchange 2010 DAG and wanted to share my work with the Exchange community.  Over time some of the databases in an Exchange 2010 DAG  will have an uneven distribution of mailboxes.  The script in this post automates the assignment of mailboxes for redistribution based on a couple of criteria, standard mailbox count, large mailbox count and total mailbox count.  These definition of standard and large mailbox sizes are different in just about every environment.  Therefore, I’m making the assumption that if a mailbox in your environment is using the default database quotas, it is a standard mailbox.  Otherwise, the mailbox is not using the default database quotas and has a different, larger quota that is uniform across the board.  The high level steps are:

  • Gather all DAG databases.
  • Gather mailboxes on each database and categorize as standard or large.
  • Make calculations about each mailbox type per DAG database so that we can get accurate tallies and then evenly redistribute mailboxes.
  • Make new-moverequest assignments and track the changes that will occur on the mailbox count per database
  • Initiate the new-moverequest for mailboxes selected.

This script will require the Exchange 2010 snapin.

 Microsoft.Exchange.Management.PowerShell.E2010 -ErrorAction "SilentlyContinue"

Set a variable for the new-moverequest batch name.

$BatchName = RebalanceDAG

Get the databases within the DAG but skip recovery databases. Hopefully this makes the database gather process as generic as possible.

# Get all the DAG databases
$TarDatabases = Get-MailboxDatabase | where {$_.mastertype `
-eq "DatabaseAvailabilityGroup" -and $_.Recovery -eq $False}

We’ll use $DBCountArray for tracking the mailbox count on each database. $MBXArray will be used to store every mailbox in your organization and leveraged to make each new-moverequest.

# Create empty arrays to store sorting data.  One for Database counts and one `
#  for mailbox types and move request assignments.
$DBCountArray = @()
$MBXArray = @()

In this next code block we are taking each DAG database and then enumerating the mailboxes it contains.  This will take some time to execute so a progress bar is helpful here.  There are two variables used as counters (line 15 and 16) which are set to zero.  In the second foreach loop the script examines the current mailbox and determines if it is standard or large based on it using default database quotas or not.  The MBXObject variable records basic data about the mailbox and puts this data into the MBXArray.  At the end of the first foreach loop the script records each mailbox processed and tallies the count for each database.

# Build the list of databases with associated counts for the various criteria used during sorting.
Foreach ($TarDatabase in $TarDatabases) {
# Show a status bar for progress while data is collected.
$PercentComplete = [Math]::Round(($LoopCount++ / $TarDatabases.Count * 100),1)
$CurrentDB = $TarDatabase.Name
Write-Progress -Activity "Mailbox Database Query in Progress" -PercentComplete $PercentComplete `
-Status "$PercentComplete% Complete" -CurrentOperation "Current Database: $CurrentDB"

# Query the current database in the foreach loop and get every mailbox.
$TarDBInfo = Get-Mailbox -Database $TarDatabase

# Set the initial values to 0 for each database being processed.
$TotalActiveSTDMBs = 0
$TotalActiveLRGMBs = 0
# Loop through each mailbox in the database checking to see if it is a large mailbox or not.
Foreach ($MBXInfo in $TarDBINfo) {
$MBXObject = $null
$MBXObject = New-Object system.Object
$MBXObject | Add-Member -type NoteProperty -Name "Database" -Value $MBXInfo.database.Name
$MBXObject | Add-Member -type NoteProperty -Name "Name" -Value $MBXInfo.Name
$MBXObject | Add-Member -type NoteProperty -Name "PrimarySMTP" -Value $MBXInfo.PrimarySmtpAddress
If ($MBXInfo.UseDatabaseQuotaDefaults -eq $true) {
# It's a standard mailbox size so increment that number.
$TotalActiveSTDMBs++
$MBXObject | Add-Member -type NoteProperty -Name "MBXSize" -Value "Standard"
} Else {
# It's a large mailbox size so increment that number.
$TotalActiveLRGMBs++
$MBXObject | Add-Member -type NoteProperty -Name "MBXSize" -Value "Large"
}
$MBXObject | Add-Member -type NoteProperty -Name "MoveRequest" -Value $Null
$MBXArray += $MBXObject
# Store the collected data in the DBCountArray variable.
$DBObject = $Null
$DBObject = New-Object system.Object
$DBObject | Add-Member -type NoteProperty -Name "Database" -Value $TarDatabase
$DBObject | Add-Member -type NoteProperty -Name "StandardMailbox" -Value $TotalActiveSTDMBs
$DBObject | Add-Member -type NoteProperty -Name "LargeMailbox" -Value $TotalActiveLRGMBs
$DBObject | Add-Member -type NoteProperty -Name "TotalMailboxes" -Value ($TotalActiveSTDMBs + $TotalActiveLRGMBs)
$DBCountArray += $DBObject
}

We now take the $DBCountArray and pipe the collected counts to measure-object to get an average number for each of the three attributes; totalmailboxes, largemailbox, and standardmailbox.  Secondly use [Math] in order to round the averages to a whole number.

We’ll use all the calculated variables to continue building out what the database counts are within $DBCountArray.

# Measure the criteria counts to obtain various data. Average will be used to judge
# what each database count should be.
$TotalMBs = $DBCountArray | Measure-Object "TotalMailboxes" -Average
$TotalLMBs = $DBCountArray | Measure-Object "LargeMailbox" -Average
$TotalStdMBs = $DBCountArray | Measure-Object "StandardMailbox" -Average

# Round the averages.
$TotalMBAvg = ([Math]::Round($TotalMBs.average))
$TotalLMBAvg = ([Math]::Round($TotalLMBs.average))
$TotalStdMBAvg = ([Math]::Round($TotalStdMBs.average))

In this block the script matches the current database in the foreach loop with where-object and makes a calculation on each criteria by subtracting the average value from the total value and adding the property to the $DBCountArray.  This lets us know where each database is in relation to the average.  The calculated number will be positive integer, negative integer, or will be zero.  This will be the basis on which database to move mailboxes from and where to move them to.

# Using the averages obtained get the variance on the current database counts.
Foreach ($DB in $DBCountArray){
$DBCountArray | where {$_.database.name -eq $DB.database.Name} `
| Add-Member -type NoteProperty -Name "StdMbxDiff" -Value ($DB.Standardmailbox - $TotalStdMBAvg)
$DBCountArray | where {$_.database.name -eq $DB.database.Name} `
| Add-Member -type NoteProperty -Name "LrgMbxDiff" -Value ($DB.Largemailbox - $TotalLMBAvg)
$DBCountArray | where {$_.database.name -eq $DB.database.Name} `
| Add-Member -type NoteProperty -Name "TotMbxDiff" -Value ($DB.TotalMailboxes - $TotalMBAvg)
}

This section handles new-moverequest assignments for large mailboxes and tracking the database counts for each large mailbox.  The source databases are selected by sorting the totmbxdiff property using the descending switch.  Selecting the first one will always grab the database in the list that is farthest out of skew from the computed average.  I’ve devised a non elegant way to add and subtract each property in the array.  By using the do until code block the script nulls out the source and target during each iteration and will continue until either to source or target databases have reached zero, or in other words, until it runs out of mailboxes to move or a place to move them to.

# Loop through and assess the count on the Database count, increment the various criteria and make new move assignments.
Write-Host "Assigning Large Mailboxes" -ForegroundColor Yellow
do {
# initialiaze/null out the variables to prevent contaminating the loop.
$DBsource = $null
$DBtarget = $null
# Get the large mailbox count source and target databases
$DBsource = $DBCountArray | where {$_.lrgmbxdiff -gt 0} | sort totmbxdiff -Descending | select -First 1
$DBtarget = $DBCountArray | where {$_.lrgmbxdiff -lt 0} `
| sort totmbxdiff | select -First 1
# If they aren't null then do the work.
if ($DBsource -ne $null -and $DBtarget -ne $null){
# decrement the source databases
($DBCountArray | where {$_.database.name -eq $DBsource.database}).largemailbox = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).largemailbox -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).totalmailboxes = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).totalmailboxes -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).lrgmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).lrgmbxdiff -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).totmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).totmbxdiff -1
# increment the target databases
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).largemailbox = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).largemailbox +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totalmailboxes = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totalmailboxes +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).lrgmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).lrgmbxdiff +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totmbxdiff +1
# Access the list of mailboxes and make an assigment based on the target identified in $DBtarget
($MBXArray | where {$_.database -eq $DBsource.Database -and $_.mbxsize -eq "large" -and $_.moverequest -eq $null} | select -First 1).moverequest = $DBtarget.Database.Name
}
}
# Keep doing the loop until either variable runs out of databases.
until ($null -eq $DBtarget -or $null -eq $DBsource)

This next section of code is rinse and repeat for the standard mailboxes.

# Loop through and assess the count on the Database count, increment the various criteria and make new move assignments.
Write-Host "Assigning Standard Mailboxes" -ForegroundColor Yellow
do {
# initialiaze/null out the variables to prevent contaminating the loop.
$DBsource = $null
$DBtarget = $null
# Get the standard mailbox count source and target databases
$DBsource = $DBCountArray | where {$_.stdmbxdiff -gt 0} | sort totmbxdiff -Descending | select -First 1
$DBtarget = $DBCountArray | where {$_.stdmbxdiff -lt 0} | sort totmbxdiff | select -First 1
# If they aren't null then do the work.
if ($DBsource -ne $null -and $DBtarget -ne $null){
# decrement the source databases
($DBCountArray | where {$_.database.name -eq $DBsource.database}).standardmailbox = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).standardmailbox -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).totalmailboxes = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).totalmailboxes -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).stdmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).stdmbxdiff -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).totmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).totmbxdiff -1
# increment the target databases
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).standardmailbox = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).standardmailbox +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totalmailboxes = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totalmailboxes +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).stdmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).stdmbxdiff +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totmbxdiff +1
# access the list of mailboxes and make an assignment based on the target identified in $DBtarget
($MBXArray | where {$_.database -eq $DBsource.Database -and $_.mbxsize -eq "standard" -and $_.moverequest -eq $null} | select -First 1).moverequest = $DBtarget.Database.Name
}
}
# Keep doing the loop until either variable runs out of databases.
until ($null -eq $DBtarget -or $null -eq $DBsource)

If you have made it this far then take a peek at what has been generated in the $DBCountArray

$DBCountArray | ft -AutoSize

Taking a look at the contents of the $MBXArray you will see something similar.  This example list shows standard mailboxes but the mailboxes are not assigned a database for a move request.  The $MBXArray will be used with the new-moverequest cmdlet to direct mailboxes to their new databases.

$MBXArray

The final step is to initiate the new-move request.  This is accomplished by taking the $MBXArray and trimming out any mailboxes without the moverequest property populated using where-object.  The $MoveRequest variable contains all the mailboxes that will be moved so simply pipe that variable into a ForEach loop that creates a new move request.

# New-Move request to initiate seeding of mailboxes to databases as assigned in $MailboxData table.
$MoveRequest = $MBXArray | where {$_.moverequest -ne $null}
$MoveRequest | ForEach {
$TargetDB = $_.DatabaseName
$ID = $_.PrimarySMTPAddress
New-MoveRequest -identity $ID -TargetDatabase $TargetDB -BadItemLimit 50 -Batchname $BatchName -SuspendWhenReadyToComplete -Confirm:$false
}

Here is the script in it’s entirety:

# Get all the DAG databases
$TarDatabases = Get-MailboxDatabase | where {$_.mastertype -eq "DatabaseAvailabilityGroup" -and $_.Recovery -eq $False}

# Create empty arrays to store sorting data.  One for Database counts and one `
#  for mailbox types and move request assignments.
$DBCountArray = @()
$MBXArray = @()

# Build the list of databases with associated counts for the various criterea `
#  used durning sorting.
Foreach ($TarDatabase in $TarDatabases) {
# Show a status bar for progress while data is collected.
$PercentComplete = [Math]::Round(($LoopCount++ / $TarDatabases.Count * 100),1)
$CurrentDB = $TarDatabase.Name
Write-Progress -Activity "Mailbox Database Query in Progress" -PercentComplete $PercentComplete `
-Status "$PercentComplete% Complete" -CurrentOperation "Current Database: $CurrentDB"

# Define the query which which finds every mailbox in the database.
$TarDBInfo = Get-Mailbox -Database $TarDatabase
# Set the initial values to 0 for each database being processed.
$TotalActiveSTDMBs = 0
$TotalActiveLRGMBs = 0
# Loop through each mailbox in the database checking to see if it is a large mailbox or not
Foreach ($MBXInfo in $TarDBINfo) {
$MBXObject = $null
$MBXObject = New-Object system.Object
$MBXObject | Add-Member -type NoteProperty -Name "Database" -Value $MBXInfo.database.Name
$MBXObject | Add-Member -type NoteProperty -Name "Name" -Value $MBXInfo.Name
$MBXObject | Add-Member -type NoteProperty -Name "PrimarySMTP" -Value $MBXInfo.PrimarySmtpAddress

If ($MBXInfo.UseDatabaseQuotaDefaults -eq $true) {
# It's a standard mailbox size so increment that number.
$TotalActiveSTDMBs++
$MBXObject | Add-Member -type NoteProperty -Name "MBXSize" -Value "Standard"
} Else {
# It's a large mailbox size so increment that number.
$TotalActiveLRGMBs++
$MBXObject | Add-Member -type NoteProperty -Name "MBXSize" -Value "Large"
}
$MBXObject | Add-Member -type NoteProperty -Name "MoveRequest" -Value $Null
$MBXArray += $MBXObject
}
# Store the collected date in the DBCountArray variable.
$DBObject = $Null
$DBObject = New-Object system.Object
$DBObject | Add-Member -type NoteProperty -Name "Database" -Value $TarDatabase
$DBObject | Add-Member -type NoteProperty -Name "StandardMailbox" -Value $TotalActiveSTDMBs
$DBObject | Add-Member -type NoteProperty -Name "LargeMailbox" -Value $TotalActiveLRGMBs
$DBObject | Add-Member -type NoteProperty -Name "TotalMailboxes" -Value ($TotalActiveSTDMBs + $TotalActiveLRGMBs)
$DBCountArray += $DBObject
}

# Measure the critera counts to obtain various data. Average will be used to judge `
#  what each database count should be.
$TotalMBs = $DBCountArray | Measure-Object "TotalMailboxes" -Average -Maximum -Minimum -Sum
$TotalLMBs = $DBCountArray | Measure-Object "LargeMailbox" -Average -Maximum -Minimum -Sum
$TotalStdMBs = $DBCountArray | Measure-Object "StandardMailbox" -Average -Maximum -Minimum -Sum

# Round the averages.
$TotalMBAvg = ([Math]::Round($TotalMBs.average))
$TotalLMBAvg = ([Math]::Round($TotalLMBs.average))
$TotalStdMBAvg = ([Math]::Round($TotalStdMBs.average))

# Using the averages obtained get the variance on the current database counts.
Foreach ($DB in $DBCountArray){
# Blackberry and Large Mailbox
$DBCountArray | where {$_.database.name -eq $DB.database.Name} | Add-Member -type NoteProperty -Name "StdMbxDiff" -Value ($DB.Standardmailbox - $TotalStdMBAvg)
$DBCountArray | where {$_.database.name -eq $DB.database.Name} | Add-Member -type NoteProperty -Name "LrgMbxDiff" -Value ($DB.Largemailbox - $TotalLMBAvg)
$DBCountArray | where {$_.database.name -eq $DB.database.Name} | Add-Member -type NoteProperty -Name "TotMbxDiff" -Value ($DB.TotalMailboxes - $TotalMBAvg)
}

$DBCountArray | ft -AutoSize

# Loop through and assess the count on the Database count, increment the various `
#  criteria and make new move assignments.
Write-Host "Assigning Large Mailboxes" -ForegroundColor Yellow
do {
# initialiaze/null out the variables to prevent contaminating the loop.
$DBsource = $null
$DBtarget = $null
# Get the large mailbox count source and target databases
$DBsource = $DBCountArray | where {$_.lrgmbxdiff -gt 0} | sort totmbxdiff -Descending | select -First 1
$DBtarget = $DBCountArray | where {$_.lrgmbxdiff -lt 0} | sort totmbxdiff | select -First 1
# If they aren't null then do the work.
if ($DBsource -ne $null -and $DBtarget -ne $null){
# decrement the source databases
($DBCountArray | where {$_.database.name -eq $DBsource.database}).largemailbox = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).largemailbox -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).totalmailboxes = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).totalmailboxes -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).lrgmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).lrgmbxdiff -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).totmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).totmbxdiff -1
# increment the target databases
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).largemailbox = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).largemailbox +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totalmailboxes = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totalmailboxes +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).lrgmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).lrgmbxdiff +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totmbxdiff +1
# access the list of mailboxes and make an assigment based on the target identified in $DBtarget
($MBXArray | where {$_.database -eq $DBsource.Database -and $_.mbxsize -eq "large" -and $_.moverequest -eq $null} | select -First 1).moverequest = $DBtarget.Database.Name
}
}
# Keep doing the loop until either variable runs out of databases.
until ($null -eq $DBtarget -or $null -eq $DBsource)

$DBCountArray | ft -AutoSize

# Loop through and assess the count on the Database count, increment the various `
#  criteria and make new move assignments.
Write-Host "Assigning Standard Mailboxes" -ForegroundColor Yellow
do {
# initialiaze/null out the variables to prevent contaminating the loop.
$DBsource = $null
$DBtarget = $null
# Get the standard mailbox count source and target databases
$DBsource = $DBCountArray | where {$_.stdmbxdiff -gt 0} | sort totmbxdiff -Descending | select -First 1
$DBtarget = $DBCountArray | where {$_.stdmbxdiff -lt 0} | sort totmbxdiff | select -First 1
# If they aren't null then do the work.
if ($DBsource -ne $null -and $DBtarget -ne $null){
# decrement the source databases
($DBCountArray | where {$_.database.name -eq $DBsource.database}).standardmailbox = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).standardmailbox -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).totalmailboxes = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).totalmailboxes -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).stdmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).stdmbxdiff -1
($DBCountArray | where {$_.database.name -eq $DBsource.database}).totmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBsource.database}).totmbxdiff -1
# increment the target databases
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).standardmailbox = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).standardmailbox +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totalmailboxes = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totalmailboxes +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).stdmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).stdmbxdiff +1
($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totmbxdiff = ($DBCountArray | where {$_.database.name -eq $DBtarget.database}).totmbxdiff +1
# access the list of mailboxes and make an assigment based on the target identified in $DBtarget
($MBXArray | where {$_.database -eq $DBsource.Database -and $_.mbxsize -eq "standard" -and $_.moverequest -eq $null} | select -First 1).moverequest = $DBtarget.Database.Name
}
}
# Keep doing the loop until either variable runs out of databases.
until ($null -eq $DBtarget -or $null -eq $DBsource)

# Uncomment to double check your arrays
# $DBCountArray | ft -AutoSize
# $MBXArray | where {$_.moverequest -ne $null}

# New-Move request to initiate seeding of mailboxes to databases as assigned in $MailboxData table.
### The new-moverequest loop is commented out so you don't accidently initiate a move request
<# $MoveRequest = $MBXArray | where {$_.moverequest -ne $null} $MoveRequest | ForEach { $TargetDB = $_.DatabaseName $ID = $_.PrimarySMTPAddress New-MoveRequest -identity $ID -TargetDatabase $TargetDB -BadItemLimit 50 -Batchname $BatchName -SuspendWhenReadyToComplete -Confirm:$false } #>

5 thoughts on “Redistribute Mailboxes Across an Exchange 2010 DAG”

    • Thanks Hunter. At the very bottom of the page is an option to expand and view the entire code. The formatting isn’t great but it is the entire script. Try that out and let me know if you still need it via email.

      Reply
    • Hi Ben. It appears that there is a problem in your $MBXArray variable. Double check that it contains a value for PrimarySmtpAddress for each mailbox you are attempting to move.

      Reply
  1. Where would I put ‘ -ResultSize Unlimited ‘ at in the script? I have DBs with over 1000 mailboxes, and need to re-balance these guys

    Reply

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