Disk failure and RAID reconstruction with a hot spare disk

About this section

This section describes how the storage system reacts to a single- or double-disk failure when a hot spare disk is available.

Data ONTAP replaces failed disk with spare and reconstructs data

If a disk fails, Data ONTAP performs the following tasks:

Replaces the failed disk with a hot spare disk (if RAID-DP is enabled and double-disk failure occurs in the RAID group, Data ONTAP replaces each failed disk with a separate spare disk). Data ONTAP first attempts to use a hot spare disk of the same size as the failed disk. If no disk of the same size is available, Data ONTAP replaces the failed disk with a spare disk of the next available size up.
In the background, reconstructs the missing data onto the hot spare disk or disks
Logs the activity in the /etc/messages file on the root volume
Sends an AutoSupport message
Note
If RAID-DP is enabled, the above processes can be carried out even in the event of simultaneous failure on two disks in a RAID group.

During reconstruction, file service might slow down.

Attention
After Data ONTAP is finished reconstructing data, replace the failed disk or disks with new hot spare disks as soon as possible, so that hot spare disks are always available in the storage system. For information about replacing a disk, see Chapter 3, Disk and Storage Subsystem Management.

If a disk fails and no hot spare disk is available, contact technical support.

You should keep at least one matching hot spare disk for each disk size and disk type installed in your storage system. This allows the storage system to use a disk of the same size and type as a failed disk when reconstructing a failed disk. If a disk fails and a hot spare disk of the same size is not available, the storage system uses a spare disk of the next available size up.