Hot Spares; Figure 10 Hot Spares; Table 10 Hot Spare Installation Conditions - Fujitsu ETERNUS DX100 S4 Design Manual

2. Basic Functions
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.
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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, the most appropriate
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 prefer-
entially improve their access to hot spares.
• When an Advanced Format disk is used as the hot spare, the sector format information that
can be confirmed from the server may be changed.
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Number of Installable Hot Spares
The number of required hot spares is determined by the total number of drives.
The following table shows the recommended number of hot spares for each drive type.

Table 10 Hot Spare Installation Conditions

Model
ETERNUS DX100 S4/DX100 S3
Fujitsu Storage ETERNUS DX100 S4/DX200 S4, ETERNUS DX100 S3/DX200 S3 Hybrid Storage Systems Design Guide (Basic)
Hot spare
Failure
Total number of drives
Up to 120
1
29
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Up to 240 Up to 264
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