Hot Spares; Figure 10 Hot Spares - Fujitsu ETERNUS DX500 S4/DX600 S4 Design Manual

2. Basic Functions
RAID Functions
In the ETERNUS DX, volumes have different stripe sizes that depend on the RAID level and the stripe depth
•
parameter.
For details about the stripe sizes for each RAID level and the stripe depth parameter values, refer to "ETER-
NUS Web GUI User's Guide".
Note that the available user capacity can be fully utilized if an exact multiple of the stripe size is set for the
volume size. If an exact multiple of the stripe size is not set for the volume size, the capacity is not fully
utilized and some areas remain unused.
When a Thin Provisioning Pool (TPP) is created, a control volume is created for each RAID group that config-
•
ures the relevant TPP. Therefore, the maximum number of volumes that can be created in the ETERNUS DX
decreases by the number of RAID groups that configure a TPP.
When the Flexible Tier function is enabled, 64 work volumes are created. The maximum number of volumes
•
that can be created in the ETERNUS DX decreases by the number of work volumes that are created.
When a Flexible Tier Sub Pool (FTSP) is created, a control volume is created for each RAID group that config-
•
ures the relevant FTSP. Therefore, the maximum number of volumes that can be created in the ETERNUS DX
decreases by the number of RAID groups that configure an FTSP.
When using the VVOL function, a single volume for the VVOL management information is created the mo-
•
ment a VVOL is created. The maximum number of volumes that can be created in the ETERNUS DX decrea-
ses by the number of volumes for the VVOL management information that are created.

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 au-
tomatically selected and incorporated into a RAID group.
FUJITSU Storage ETERNUS DX500 S4/DX600 S4, ETERNUS DX500 S3/DX600 S3 Hybrid Storage Systems Design Guide (Basic)
Hot spare
Failure
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