Hot Spares; Figure 10 Hot Spares - Fujitsu ETERNUS AF250 Design Manual

1. Function
RAID Functions

Hot Spares

Hot spares are used as spare drives for when drives in a RAID group fail, or when drives are in error status.

Figure 10 Hot Spares

RAID group
When the RAID level is RAID6-FR, data in a failed drive can be restored to a reserved space in a RAID group
even when a drive error occurs because a RAID6-FR RAID group retains a reserved space for a whole drive in
the RAID group. If the reserved area is in use and an error occurs in another drive (2nd) in the RAID group,
then the hot spare is used as a spare.
■
Types of Hot Spares
The following two types of hot spare are available:
Global Hot Spare
•
This is available for any RAID group. When multiple hot spares are installed, a drive is automatically selected
and incorporated into a RAID group.
Dedicated Hot Spare
•
This is only available to the specified RAID group (one RAID group).
The Dedicated Hot Spare cannot be registered in a RAID group that is registered in TPPs, FTRPs, or REC Disk
Buffers.
Assign "Dedicated Hot Spares" to RAID groups that contain important data, in order to preferentially improve
their access to hot spares.
■
Number of Installable Hot Spares
Installing at least one hot spare is recommended.
■
Types of Drives
If a combination of SSDs and SED SSDs is installed in the ETERNUS AF, each different type of drive requires a
corresponding hot spare. The capacity of each hot spare must be equal to the largest capacity of the same-type
drives.
Hot spare
Failure
FUJITSU Storage ETERNUS AF250 S2, ETERNUS AF250 All-Flash Arrays Design Guide (Basic)
Copyright 2019 FUJITSU LIMITED
27
P3AG-1822-09ENZ0