When increasing an Exchange 2010 mailbox from 2GB to 10GB, several technical factors must be evaluated:

• Database I/O patterns change significantly with larger mailboxes
• OST file synchronization becomes more resource-intensive
• Backup/Restore times increase exponentially

The Exchange 2010 storage calculator reveals that 10GB mailboxes require:

# Sample IOPS calculation
$mailboxCount = 1
$mailboxSizeGB = 10
$ioPerGB = 0.15 # Standard for Exchange 2010
$baseIOPS = 100 # Server baseline

$requiredIOPS = $baseIOPS + ($mailboxCount * $mailboxSizeGB * $ioPerGB)
Write-Host "Estimated IOPS requirement: $requiredIOPS"

Outlook clients may experience these specific issues:

• OST file corruption risk increases above 5GB
• Search indexing becomes slower
• Calendar performance degrades

A PowerShell snippet to monitor OST health:

Get-ChildItem $env:localappdata\Microsoft\Outlook\*.ost | 
Select Name,@{Name="SizeGB";Expression={[math]::Round($_.Length/1GB,2)}}

Instead of simply increasing the limit, consider implementing:

1. Archive mailbox with retention policies
2. Cloud-based archiving solution
3. Mailbox folder quotas

Example retention policy implementation:

New-RetentionPolicyTag "Executives-1Year" -Type All -AgeLimitForRetention 365 -RetentionAction DeleteAndAllowRecovery
New-RetentionPolicy "ExecutivePolicy" -RetentionPolicyTagLinks "Executives-1Year"
Set-Mailbox "CEO" -RetentionPolicy "ExecutivePolicy"

Essential performance counters to watch:

When expanding Exchange 2010 mailboxes beyond Microsoft's recommended 2GB threshold, we must consider several architectural constraints. The ESE (Extensible Storage Engine) database that powers Exchange has specific performance characteristics with large item counts.

A 10GB mailbox in Exchange 2010 typically contains 20,000-50,000 items. This impacts:

// PowerShell command to check current mailbox statistics
Get-MailboxStatistics -Identity "BOSS" | 
Select DisplayName,ItemCount,TotalItemSize,Database

Key storage metrics to monitor:

• Database cache hit ratio (should be >90%)
• Average disk read latency (<20ms)
• Background database maintenance cycles

Outlook 2010/2013 in cached mode with a 10GB OST file presents challenges:

// Registry tweak for large OST files (Outlook 2010)
Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\OST]
"MaxLargeFileSize"=dword:00005000

Large mailboxes affect:

• ESEUTIL repair operations (increased duration)
• Backup window requirements (VSS snapshots)
• Database portability during hardware refreshes

Instead of a single large mailbox, consider:

# Archive policy configuration example
New-RetentionPolicyTag -Name "1YearArchive" -Type All -AgeLimitForRetention 365 
-RetentionAction MoveToArchive -MessageClass *

Essential performance counters to track:

• MSExchangeIS\RPC Average Latency
• MSExchangeIS\RPC Requests
• PhysicalDisk(*)\Avg. Disk sec/Read