Fast Recovery; Figure 15 Fast Recovery - Fujitsu ETERNUS DX100 S4 Design Manual

2. Basic Functions
Data Protection

Fast Recovery

This function recovers data quickly by relocating data in the failed drive to the other remaining
drives when a drive error is detected.
For a RAID group that is configured with RAID6-FR, Fast Recovery is performed for the reserved
area that is equivalent to hot spares in the RAID group when a drive error occurs.
If a second drive fails when the reserved area is already used by the first failed drive, a normal re-
build (hot spare rebuild in the ETERNUS DX) is performed.
For data in a failed drive, redundant data and reserved space are allocated in different drives ac-
cording to the area. A fast rebuild can be performed because multiple rebuild processes are per-
formed for different areas simultaneously.

Figure 15 Fast Recovery

RAID6-FR (No redundancy)
RAID6-FR (Redundant)
For the Fast Recovery function that is performed when the first drive fails, a copyback is per-
formed after the failed drive is replaced even if the Copybackless function is enabled.
For a normal rebuild process that is performed when the reserved space is already being used
and the second drive fails, a copyback is performed according to the settings of the Copyback-
less function.
Fujitsu Storage ETERNUS DX100 S4/DX200 S4, ETERNUS DX100 S3/DX200 S3 Hybrid Storage Systems Design Guide (Basic)
High Speed Rebuilding
(Creating data and writing to the FHS area
simultaneously)
Failure
RAID6-FR ((3D+2P) × 2 + 1HS)
Disconnect
RAID6-FR ((3D+2P) × 2)
Copyright 2023 Fujitsu Limited
A failed drive is disconnected from
the ETERNUS storage system.
Data is created from the redundant
data in normal drives and written to
reserved space (FHS) in RAID6-FR.
Failed drive
35
: Redundant data for area A
of the failed drive
: Redundant data for area B
of the failed drive
: Fast recovery Hot Spare (FHS)
P3AM-7642-32ENZ0