Table 8 Hot Spare Selection Criteria - Fujitsu ETERNUS DX60 S4 Design Manual

1. Function
RAID Functions
■
Types of Drives
If a combination of SAS disks, Nearline SAS disks, and SSDs is installed in the ETERNUS DX, each different type of
drive requires a corresponding hot spare.
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.
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, the following criteria are used to select which hot spare will re-
place a failed drive:

Table 8 Hot Spare Selection Criteria

Selection or-
Selection criteria
der
1 A hot spare with the same type, same capacity, and same rotational speed as the failed drive
2 A hot spare with the same type and same rotational speed as the failed drive but with a larger capacity (*1)
3 A hot spare with the same type and same capacity as the failed drive but with a different rotational speed
4 A hot spare with the same type as the failed drive but with a larger capacity and a different rotational speed (*1)
*1: When there are multiple hot spares with a larger capacity than the failed drive, the hot spare with the
smallest capacity among them is used first.
FUJITSU Storage ETERNUS DX60 S4, ETERNUS DX60 S3 Hybrid Storage Systems Design Guide (Basic)
25
Copyright 2019 FUJITSU LIMITED
P3AM-8992-14ENZ0