User Capacity (Logical Capacity); Table 3 Formula For Calculating User Capacity For Each Raid Level; Table 4 User Capacity Per Drive - Fujitsu ETERNUS AF250 Design Manual

1. Function
RAID Functions
■
Recommended RAID Level
Recommended RAID levels are RAID5 and RAID6.
For SSDs, a RAID5 configuration or a fault tolerant enhanced RAID6 configuration is recommended because SSDs
operate much faster than other types of drive. For large capacity SSDs, using a RAID6-FR configuration, which
provides excellent performance for the rebuild process, is recommended.

User Capacity (Logical Capacity)

User Capacity for Each RAID Level
The user capacity depends on the capacity of drives that configure a RAID group and the RAID level.
Table 3 shows the formula for calculating the user capacity for each RAID level.

Table 3 Formula for Calculating User Capacity for Each RAID Level

RAID level
RAID0
RAID1
RAID1+0
RAID5
RAID5+0
RAID6
RAID6-FR
*1: "N" is the number of RAID6 configuration sets. For example, if a RAID6 group is configured with "(3D+2P)
´2+1HS", N is "2".
User Capacity of Drives
Table 4 shows the user capacity for each drive.

Table 4 User Capacity per Drive

Product name (*1)
400GB SSD
960GB SSD
1.92TB SSD
3.84TB SSD
7.68TB SSD
15.36TB SSD
30.72TB SSD
*1: The capacity of the product names for the drives is based on the assumption that 1MB = 1,000
while the user capacity for each drive is based on the assumption that 1MB = 1,024
OS file management overhead will reduce the actual usable capacity.
The user capacity is constant regardless of the encryption support (SED).
Formula for user capacity computation
Drive capacity ´ Number of drives
Drive capacity ´ Number of drives ¸ 2
Drive capacity ´ Number of drives ¸ 2
Drive capacity ´ (Number of drives - 1)
Drive capacity ´ (Number of drives - 2)
Drive capacity ´ (Number of drives - 2)
Drive capacity ´ (Number of drives - (2 ´ N) - Number of hot spares) (*1)
FUJITSU Storage ETERNUS AF250 S2, ETERNUS AF250 All-Flash Arrays Design Guide (Basic)
Copyright 2019 FUJITSU LIMITED
User capacity
374,528MB
914,432MB
1,830,144MB
3,661,568MB
7,324,416MB
14,650,112MB
29,301,504MB
22
2
bytes,
2
bytes. Furthermore,
P3AG-1822-09ENZ0