How Storage Spaces Makes Use of Hot Spares

Article
08/31/2016

Applies To: Windows Server 2012

This topic describes how to designate disks as hot spares for use in automatically replacing failed disks in a storage pool, and how Storage Spaces monitors disk health and automatically recovers from failed disks.

How to designate hot spares

You can designate a disk as a hot spare when creating a storage pool or when adding disks to a pool by using the File and Storage Services role in Server Manager, or by using Windows PowerShell.

When creating a storage pool

To designate one or more disks as hot spares when creating a storage pool, use the following procedure:

Create a storage pool with hot spares

In Server Manager, click File and Storage Services, and then Storage Pools.
In the STORAGE POOLS tile, click Tasks, and then New Storage Pool.
On the Select physical disks for the storage pool page, select the disks you want to designate as hot spares, and then choose Hot Spare in the Allocation column.

When adding a physical disk

To designate one or more disks as hot spares when adding physical disks to a storage pool, use the following procedure:

Add a hot spare to a storage pool

In Server Manager, click File and Storage Services, and then Storage Pools.
Select the appropriate storage pool, and then in the PHYSICAL DISKS tile, click Tasks, and then Add Physical Disk.
Select the disks you want to designate as hot spares, and then choose Hot Spare in the Allocation column.

Windows PowerShell equivalent commands

The following Windows PowerShell cmdlet or cmdlets perform the same function as the preceding procedure. Enter each cmdlet on a single line, even though they may appear word-wrapped across several lines here because of formatting constraints.

The following example adds the physical disk named PhysicalDisk4 to the Company Data storage pool and designates the disk as a hot spare.

Add-PhysicalDisk -StoragePoolFriendlyName "Company Data" -PhysicalDisks (Get-PhysicalDisk -FriendlyName PhysicalDisk4) -Usage HotSpare

How Storage Spaces monitors disk health

Write errors

If a disk reports a media error during a write operation, Storage Spaces performs the following actions:

Marks the disk as Failed
Activates the failure LED for the disk, if the disk is in a JBOD that supports SCSI Enclosure Services
Replaces the failed disk with a hot spare and retries the write operation, if there is a hot spare available in the storage pool

Note

Modern hard disks are designed to silently handle a limited number failures without reporting an error to the operating system. If the disk exceeds the number of allowed failures during a write operation, it reports a media error, which is typically an indicator that the disk is approaching a catastrophic failure.

Read errors

If an error occurs while reading data from a disk, Storage Spaces performs the following actions:

Attempts to retrieve a copy of the data from another disk in the mirror or parity space. If this attempt succeeds, the read error is cleared.
Attempts to write a fresh copy of the data that was retrieved to the location that produced the read error. If this attempt fails, Storage Spaces produces a write error and takes action as described in the Write Errors section.

Disconnected disks

If a disk is unexpectedly disconnected or silently fails read or write operations and a hot spare is available in the storage pool Storage Spaces performs the following actions by default:

Marks the disk as Failed
Replaces the failed disk with a hot spare and retries the write operation
If there is not a hot spare available, Storage Spaces waits for the disk to reconnect or for administrator to take action.

This behavior is configurable by using the Set-StoragePool –RetireMissingPhysicalDisks <value> cmdlet from a Windows PowerShell session. There are three settings:

Setting	Behavior
Auto	If a hot spare is available in the storage pool follow the Enabled logic. Otherwise, follow the Disabled logic.
Enabled	Mark the disk as Failed, replace it with a hot spare, and then retry the operation
Disabled	Wait for the disk to reconnect or for an administrator to take action (do not use any available hot spares)