- Notes, cautions, and warnings
- Introduction
- Terminology
- Hardware best practices
- Networking best practices
- Windows Server 2012 R2 best practices
- Microsoft Storage Spaces best practices
- Cluster best practices
- Scale-Out File Server best practices
- Converged best practices
- Getting help
Dell Storage with Microsoft Storage Spaces Best Practices Guide
Configuring storage pools for rebuilds
Microsoft Storage Spaces automatically rebuilds VDs by using free disk space and does not require assigning hot-spares. If a physical disk fails, the failed physical disk is regenerated from free storage disk space without user’s intervention. The rebuild begins immediately after a disk failure is detected, limiting the exposure to additional physical disk failure while the VD is running in a degraded state. Dell recommends that you enable automatic rebuilds.
Run the following PowerShell command to enable automatic rebuilds (configured for each pool).
Set-StoragePool –FriendlyName <poolName> -RetireMissingPhysicalDisks Always
- NOTE: Before performing maintenance operations, and when storage pools are configured to automatic rebuild, prior to turning off a storage enclosure, you must change the RetireMissingPhysicalDisks attribute of all affected storage pools to Never. When the network communication with the drive becomes unavailable because the storage enclosure was turned off for maintenance, changing the attributes prevents the VDs from immediately initiating rebuilds. Ensure that you change RetireMissingPhysicalDisks back to the original value after the maintenance operations completes.
When a storage pool is configured for automatic rebuilds, it is important to maintain sufficient free disk space in each pool to enable VDs to automatically rebuild in the event of a physical disk failure. Sufficient free disk space is equal to the capacity of one HDD plus an additional 8 GB (for storage spaces overhead) multiplied by the number of disk failures to automatically recover from the storage pool’s HDD tier, and the capacity of one SSD plus an additional 8 GB (for storage spaces overhead) multiplied by the number of disk failures to automatically recover from the SSD tier. Equations for sizing the HDD and SSD tiers are specified in the Storage Tiers section in this document.
There are two types of rebuild methods — parallel and sequential. During a parallel rebuild process, the data required to rebuild is obtained from multiple physical disks in the pool. Parallel rebuilds are very fast and reduce the time a VD is in a degraded state. However, because of multiple physical disks sourcing the repair data, there is some impact to storage I/O performance during rebuilds. A sequential rebuild only sources repair data from one physical disk in the pool at a time. This means that there is less impact to storage I/O performance during rebuilds. However, the rebuild process takes longer.
Dell recommends parallel rebuilds because it provides the fastest
method to ensure all VDs return to their full resiliency. To optimize
VD repairs the Microsoft November 2014 KB rollup (KB3000850) is required
on all storage and compute nodes. Also, you must perform the tasks
listed in the following URL:
https://technet.microsoft.com/en-us/library/dn858079.aspx
Run one of the following PowerShell commands for configuring the rebuild method (configured for each pool).
Set-StoragePool –FriendlyName <poolName> –RepairPolicy Parallel
Set-StoragePool –FriendlyName <poolName> –RepairPolicy Sequential
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