User Manual

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failure, you must add a second disk that is at least as large as the first. It can be added
while the system is running.
X-RAID uses the capacity of one disk for data storage and reserves the capacity of a
second disk for data protection, which allows the volume to recreate data if a disk fails.
In a two-disk system, the usable storage space is one disk. In a three-disk system, the
usable storage space is two disks. In general, the total capacity of your storage system
equals the capacity of all your disks minus the capacity of one disk.
The following figure illustrates how X-RAID uses new disks.
Figure 4. X-RAID disk usage
1. The first disk that you install is used for initial (unprotected) storage space.
2. The second disk that you install is reserved for data protection (parity information).
3. Installing additional disks increases your storage space.
Note: For systems with six or fewer bays, X-RAID reserves the capacity of one disk for
data protection. For systems with more than six bays, with at least two disks and up to
five disks, X-RAID reserves the capacity of one disk for data protection. For systems with
six or more disks, the default format is RAID 6, which reserves two disks. The actual
space reserved for data protection is distributed across all disks.
Flex-RAID
Software Manual26Volume Configuration
ReadyNAS OS 6.10