Microsoft’s Resilient File System (ReFS) was introduced with Windows Server 2012. ReFS is not a direct replacement for NTFS, and is missing some underlying NTFS features, but is designed to be (as the name suggests) a more resilient file system for extremely large amounts of data.
ReFS maintains high degree of compatibility with NTFS while providing enhanced data verification and auto-correction techniques as well as an integrated end-to-end resiliency to corruptions especially when used in conjunction with the storage spaces feature.
One example that springs to mind for extremely large amounts of data is Exchange databases, which have a theoretical maximum of 16TB per database file. In reality of course we tend to run much smaller database sizes. Microsoft reportedly uses 2TB as their ideal maximum database size in Exchange Online. In customer environments I’ve worked in the trend is towards more, smaller databases such as 200GB maximum for single server scenarios, and 500GB maximum for multi-server high availability (database availability group) deployments. Even falling well short of the 16TB maximum a 2TB or even 500GB database file is still “big”.
Support for ReFS with Exchange Server
From Exchange Server 2013 and upwards (which includes Exchange Server 2016 today) Microsoft supports the use of ReFS for Exchange servers, and in fact they now recommend it as the preferred file system for Exchange Server 2016, within the following guidelines.
For Exchange Server 2013:
- ReFS is supported for volumes containing Exchange database files, log files, and content index files.
- ReFS is not supported for volumes containing Exchange binaries (the program files).
- ReFS is not supported for volumes containing the system partition.
- ReFS data integrity features must be disabled for the database (.edb) files or the entire volume that hosts database files.
- Hotfix KB2853418 must be installed.
- For Windows 2012, the following hotfixes must be installed:
This means that you should continue to use NTFS for your operating system and Exchange Server 2013 installation volume, but you can consider using ReFS for the volumes hosting Exchange databases, log files, and index files.
For Exchange Server 2016:
- ReFS is supported for volumes containing Exchange database files, log files, and content index files.
- ReFS is not supported for volumes containing Exchange binaries (the program files).
- ReFS is not supported for volumes containing the system partition.
- ReFS data integrity features are recommended to be disabled.
- For Windows 2012, the following hotfixes must be installed:
This means that you should continue to use NTFS for your operating system and Exchange Server 2016 installation volume, and it is recommended ReFS for the volumes hosting Exchange databases, log files, and index files. Note also that at this time there is no guidance directing you to disable ReFS data integrity features or install additional hotfixes when using ReFS with Exchange Server 2016. Updated the guidance above with some additional information that is expected to be added to TechNet soon.
Creating an ReFS Formatted Volume
In Windows Server 2012 or R2 during the New Volume Wizard when you get to the step for configuring File System Settings change the file system from NTFS to ReFS.
However, using the New Volume Wizard does not give you the option to disable data integrity at the volume level. To set it at the volume level itself use PowerShell when configuring new volumes. On my demo server disk 3 has been added to the server and is ready to initialize and format with ReFS.
PS C:\> Get-Disk
Number Friendly Name OperationalStatus Total Size Partition Style
------ ------------- ----------------- ---------- ---------------
2 Microsoft Virtual Disk Online 100 GB GPT
1 Microsoft Virtual Disk Online 100 GB GPT
3 Microsoft Virtual Disk Online 100 GB RAW
0 Virtual HD ATA Device Online 95 GB MBR
PS C:\> Get-Disk 3 | Initialize-Disk -PartitionStyle GPT -PassThru | New-Partition -UseMaximumSize | Format-Volume -FileSystem REFS -NewFileSystemLabel Volume3 -SetIntegrityStreams $false
Confirm
Are you sure you want to perform this action?
Warning, all data on the volume will be lost!
[Y] Yes [A] Yes to All [N] No [L] No to All [S] Suspend [?] Help (default is "Y"): y
DriveLetter FileSystemLabel FileSystem DriveType HealthStatus SizeRemaining Size
----------- --------------- ---------- --------- ------------ ------------- ----
Volume3 ReFS Fixed Healthy 99.31 GB 99.81 GB
Additional Considerations
When you are deploying an Exchange 2016 database availability group and using Autoreseed the disk reclaimer needs to know which file system to use when formatting spare disks.
C:\> Set-DatabaseAvailabilityGroup NameOfYourDAG -FileSystem ReFS
For Exchange Server 2013 DAGs, manually format the spare volumes with ReFS.
Summary
If you are running Exchange Server 2013 on Windows Server 2012/R2 today and you are using NTFS volumes then the effort to provision new ReFS volumes and migrate your data likely exceeds the benefits of ReFS over NTFS for that scenario. If you’re deploying a new Exchange Server 2013 server today you can consider using ReFS within the support guidelines mentioned in the article above.
For Exchange Server 2016 deployments ReFS is now the recommended file system, so you should plan any new deployments to use ReFS volumes for Exchange databases, log files, and content indexes.
References:
- Exchange 2013 storage configuration options
- Exchange 2016 Preferred Architecture
- Exchange Storage for Insiders: It’s ESE (Ignite video)
Thanks to Ross Smith IV from Microsoft for helping to clarify some of the missing and fragmented information on this topic.
This article Resilient File System (ReFS) and Microsoft Exchange Server is © 2015 ExchangeServerPro.com
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