functions/Get-SqlMaxMemory.ps1

Function Get-SqlMaxMemory
{
<#
.SYNOPSIS
Displays information relating to SQL Server Max Memory configuration settings. Works on SQL Server 2000-2014.

.DESCRIPTION
Inspired by Jonathan Kehayias's post about SQL Server Max memory (http://bit.ly/sqlmemcalc), this script displays a SQL Server's:
total memory, currently configured SQL max memory, and the calculated recommendation.

Jonathan notes that the formula used provides a *general recommendation* that doesn't account for everything that may be going on in your specific environment.

THIS CODE IS PROVIDED "AS IS", WITH NO WARRANTIES.

.PARAMETER SqlServer
Allows you to specify a comma separated list of servers to query.

.PARAMETER SqlCredential
Allows you to login to servers using SQL Logins as opposed to Windows Auth/Integrated/Trusted. To use:

$cred = Get-Credential, this pass this $cred to the param.

Windows Authentication will be used if DestinationSqlCredential is not specified. To connect as a different Windows user, run PowerShell as that user.

.NOTES
Author : Chrissy LeMaire (@cl), netnerds.net
Requires: sysadmin access on SQL Servers

dbatools PowerShell module (https://dbatools.io, clemaire@gmail.com)
Copyright (C) 2016 Chrissy LeMaire

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.

.LINK
https://dbatools.io/Get-SqlMaxMemory

.EXAMPLE
Get-SqlMaxMemory -SqlServer sqlcluster,sqlserver2012

Get Memory Settings for all servers within the SQL Server Central Management Server "sqlcluster"

.EXAMPLE
Get-SqlMaxMemory -SqlServer sqlcluster | Where-Object { $_.SqlMaxMB -gt $_.TotalMB } | Set-SqlMaxMemory

Find all servers in CMS that have Max SQL memory set to higher than the total memory of the server (think 2147483647)

#>

    [CmdletBinding()]
    Param (
        [parameter(Position = 0, Mandatory = $true, ValueFromPipeline = $True)]
        [Alias("ServerInstance", "SqlInstance", "SqlServers")]
        [string[]]$SqlServer,
        [System.Management.Automation.PSCredential]$SqlCredential
    )
    
    PROCESS
    {
        $collection = @()
        foreach ($servername in $sqlserver)
        {
            try
            {
                # Get number of instances running
                $ipaddr = Resolve-SqlIpAddress $servername
                $sqls = Get-Service -ComputerName $ipaddr | Where-Object { $_.DisplayName -like 'SQL Server (*' -and $_.Status -eq 'Running' }
                $sqlcount = $sqls.count
            }
            catch
            {
                Write-Warning "Couldn't get accurate SQL Server instance count. Defaulting to 1."
                $sqlcount = 1
            }
            
            Write-Verbose "Attempting to connect to $servername"
            try
            {
                $server = Connect-SqlServer -SqlServer $servername -SqlCredential $SqlCredential
            }
            catch
            {
                Write-Warning "Can't connect to $servername or access denied. Skipping."
                continue
            }
            
            $maxmem = $server.Configuration.MaxServerMemory.ConfigValue
            
            $reserve = 1
            $totalMemory = $server.PhysicalMemory
            
            
            # Some servers underreport by 1MB.
            if (($totalmemory % 1024) -ne 0) { $totalMemory = $totalMemory + 1 }
            
            if ($totalMemory -ge 4096)
            {
                $currentCount = $totalMemory
                while ($currentCount/4096 -gt 0)
                {
                    if ($currentCount -gt 16384)
                    {
                        $reserve += 1
                        $currentCount += -8192
                    }
                    else
                    {
                        $reserve += 1
                        $currentCount += -4096
                    }
                }
                $recommendedMax = [int]($totalMemory - ($reserve * 1024))
            }
            else
            {
                $recommendedMax = $totalMemory * .5
            }
            
            $recommendedMax = $recommendedMax/$sqlcount
            
            $object = New-Object PSObject -Property @{
                Server = $server.name
                TotalMB = $totalMemory
                SqlMaxMB = $maxmem
                InstanceCount = $sqlcount
                RecommendedMB = $recommendedMax
            }
            $server.ConnectionContext.Disconnect()
            $collection += $object
        }
        return ($collection | Sort-Object Server | Select-Object Server, TotalMB, SqlMaxMB, InstanceCount, RecommendedMB)
    }
}