{"id":66929,"date":"2020-11-18T07:59:33","date_gmt":"2020-11-18T07:59:33","guid":{"rendered":"https:\/\/www.stellarinfo.com\/blog\/?p=66929"},"modified":"2026-01-05T11:39:55","modified_gmt":"2026-01-05T11:39:55","slug":"defrag-exchange-mailbox-database","status":"publish","type":"post","link":"https:\/\/www.stellarinfo.com\/blog\/defrag-exchange-mailbox-database\/","title":{"rendered":"Defrag Exchange Mailbox Database using Eseutil \/d PowerShell"},"content":{"rendered":"

In Microsoft Exchange Server, the database size increases as more mailboxes are created, and data is generated by the users as they send\/receive emails.<\/p>

When some mail items are deleted from the mailboxes or mailboxes are removed from the Exchange databases, the free storage left by deleted items is not reclaimed.<\/p>

For instance, if the database size is 10GB and you remove a mailbox ~2GB, the database will remain 10GB. The 2GB space left by the deleted mailbox is called ‘White Space<\/strong>.’  <\/p>

Thus, it’s important and a best practice to reclaim the White Space by defragmenting the Exchange database. It will reduce the database size and help prevent database corruption issues caused by low or no storage.<\/p>

Why Defrag Exchange Mailbox Database?<\/strong><\/h2>

Defragmentation is a process of cleaning all unused storage or reclaiming White Space from the database, removing data fragments, and arranging the information in the contiguous regions for quick access.<\/p>

From the performance point of view, defragmentation (Eseutil \/d) makes the database access faster as the Exchange Server would not have to process a large file in memory or open and search the file, which can incur a large number of input\/output from the storage for nothing.<\/p>

Another thing is the operation of the server. As you may know, Exchange Server is sensitive about the database’s health if there is no storage or a shortage.<\/p>

Databases tend to fill the hard drive with unused space or log files. If the storage is not increased or logs are not purged, it can damage the database and lead to corruption. As a result, the Exchange database will dismount, breaking the client-server connectivity and preventing the users from sending or receiving emails<\/p>

So, it would be wise to set a schedule to check the database state periodically, depending on the size and number of users. A corrupted database can cause loss of data, service, and business.<\/p>

Things to Remember Before Defragging Exchange Mailbox Database using Eseutil \/d<\/strong><\/h2>

Before running Eseutil \/d command to defragment the Exchange database, ensure the following:<\/p>

    \n
  1. To defrag an Exchange Server database, the database must be dismounted. Unfortunately, this means that the users will be unable to access their mailboxes during this operation.<\/li>\n\n\n\n
  2. Exchange database defragmentation should be executed only after office hours as it might take some time to finish (depending on the database size and the server\/storage).  <\/li>\n\n\n\n
  3. It is highly recommended to back up the database before defragmentation for those just-in-case<\/em> scenarios.<\/li>\n\n\n\n
  4. Ensure the drive where the database is stored has enough free storage space, which is equivalent to or larger than the database size (preferably 1.1x or 1.2x size of the database). If you are short on storage capacity, this could cause a problem.<\/li>\n<\/ol>

    To calculate the required space, you must check the database size in your Exchange Server that requires defragmentation. To do so, you can use the Get-MailboxDatabase<\/strong> PowerShell cmdlet<\/a>, as given below.<\/p>

    Get-MailboxDatabase -Status | ft name, database size, availablenewmailboxspace –auto<\/code><\/pre>
    The output will display the database Name<\/strong>, the DatabaseSize,<\/strong> and the AvailableNewMailboxSpace<\/strong>.<\/p>
    \"get<\/figure>
    As you can see from the above example, the Mailbox Database 0954395982<\/strong> has a size of 247.9 MB.<\/p>
    On the other hand, it also has 74.34 MB of White Space. Of course, this is a small database with a few mailboxes. But on larger databases, defrag (Eseutil \/d) will make significant performance improvements on the disks and operation of the server.<\/p>
    You can use the following formulae to calculate the total free space required to defragment the Exchange mailbox database.<\/p>