Table 9 Hot Spare Installation Conditions - Fujitsu ETERNUS DX500 S4/DX600 S4 Design Manual

2. Basic Functions
RAID Functions
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
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 9 Hot Spare Installation Conditions

Model
ETERNUS DX500 S4/DX500 S3
ETERNUS DX600 S4/DX600 S3
■
Types of Drives
If a combination of SAS disks, Nearline SAS disks, SSDs, and SEDs is installed in the ETERNUS DX, each different
type of drive requires a corresponding hot spare.
2.5" and 3.5" drive types are available. The drive type for high-density drive enclosures is 3.5".
There are two types of rotational speeds for SAS disks; 10,000rpm and 15,000rpm. If a drive error occurs and a
hot spare is configured in a RAID group with different rotational speed drives, the performance of all the drives
in the RAID group is determined by the drive with the slowest rotational speed. When using SAS disks with dif-
ferent rotational speeds, prepare hot spares that correspond to the different rotational speed drives if required.
Even if a RAID group is configured with SAS disks that have different interface speeds, performance is not affec-
ted.
There are two types of interface speeds for SSDs; 6Gbit/s and 12Gbit/s. If a drive error occurs and a hot spare is
configured in a RAID group with different interface speed SSDs, the performance of all the SSDs in the RAID
group is determined by the SSDs with the slowest interface speed. Preparing SSDs with the same interface speed
as the hot spare is recommended.
The capacity of each hot spare must be equal to the largest capacity of the same-type drives.
■
Selection Criteria
When multiple Global Hot Spares are installed, among the drives that match the selection criteria in the order of
priority for Condition 1, drives that match the selection criteria in the order of priority for Condition 2 are auto-
matically selected as a hot spare to replace the failed drive.
If different drive types or capacities are mixed, the recommended action is to install a hot spare for each dif-
ferent drive type or capacity on each path.
FUJITSU Storage ETERNUS DX500 S4/DX600 S4, ETERNUS DX500 S3/DX600 S3 Hybrid Storage Systems Design Guide (Basic)
Total number of drives
Up to 120 Up to 240 Up to 480
1 2 4
1 2 4
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Up to 720 Up to 960 Up to 1056
6 — —
6 8 9
P3AM-7722-25ENZ0