2. M310 Component Selection (15)
(4-7) Hot Spare Disk
When assigning hot spare disks:
• Assigning a hot spare disk enables automatic restoration of data without waiting for a maintenance
service agent in the event of disk failure. Data redundancy is recovered when restoring the data to
the hot spare.
• M-Series has a “Preventive maintenance function” that moves data to hot spare disks before a disk
failure occurs by detecting symptoms of the failure in order to maintain redundancy.
• It is strongly recommended to assign a hot spare disk in order to enhance the availability of disk array
units.
• M-Series has a global hot spare function which enables hot spare disks to be used with any
HDD/SSD.
• SSD hot spare is only good with SSDs. SSD cannot be used as a hot spare with HDDs. Likewise,
HDD cannot be used as a hot spare with SSDs.
• When multiple types of disk drives are defined as hot spare disks, the priority is as follows.
1. The same interface, the same capacity and the same rotation speed as the base disk drive*.
2. The same interface, the same capacity as the base disk drive* but the slower disk used first
when multiple speeds of hot spare drives exist.
3. The same interface as the base disk drive*, but larger than the base disk drive*. When multiple
sizes of hot spare disks exist, the smaller disk is used first.
* Base disk drive = disk drive with the smallest capacity/slowest rotation speed in the pool.
• The number of recommended hot spares varies depending on the disk drive type. Refer to the table
below.
Disk drive type
Condition
Recommendation
SAS Disk Drive
One type of capacity/rotation speed
One hot spare drive / 24 disk drives
n types of capacity/rotation speed
n spare disk drives / 24 disk drives
NL-SAS Disk Drive *
1
One type of capacity/rotation speed
One hot spare drive / 12 disk drives
n types of capacity/rotation speed
n spare disk drives / 12 disk drives
SAS SSD
Hot spare is optional. Because SAS SSD does not have mechanical parts
such as motors, heads and media, it is reliable. Assign hot spare disks as a
customer requests.
Refer to “5. Functions <Hot Spare Disk>” for more details about hot spare disks.
*1
Must assign hot spare disks when NL-SAS disk drives are in the system.
<Example>
Data
HSP
Data
Data
Data
Data
Data
Data
Data
Data
Data
Data
11 x Data disks
1 x Hot spare disk
45
NEC Confidential
23 x Data disks
1 x Hot spare disk
HSP: Hot spare disk
Data: Data disk
D
ata
D
ata
D
ata
D
ata
H
S
P
D
ata
D
ata
・・・
