Volume Status - ZyXEL Communications NSA-2400 User Manual

Chapter 7 Storage Screens
• one RAID 5 volume
7.3.1.4 Four Disks
In addition to the JBOD, RAID 0 and RAID 1 choices, you may choose RAID 10, RAID 5 or
RAID5_(3 + hot-spare). With four disks you could create:
• up to four JBOD volumes
• one or two JBOD volumes and one RAID 0 or RAID 1 volume
• two RAID 0 volumes or two RAID 1 volumes
• one RAID 0 volume and one RAID 1 volume
• one RAID 5 volume (with three disks) and one JBOD volume
• one volume using one of RAID 10, RAID 5 or RAID5_(3 + hot-spare)
• Choose RAID 10 for maximum data security but with just 50% of the available space
for your data. You can recover all data even if two disks (not in the same RAID 1
array) fail. If two disks in the same RAID 1 array fail, then all data in the volume is
lost. If two disks in different RAID 1 arrays fail, then you effectively have a RAID 0
configuration.
• Choose RAID 5 if you need more disk space available for data and if up to one disk
failure is acceptable. RAID 5 uses 75% of the available space for your data. All data
can be recovered if one disk fails. If two disks fail then, all data in the volume is lost.
If one disk fails, the volume is degraded and will perform more slowly than a healthy
volume. You should shut down the NSA, replace the faulty disk and then
resynchronize the volume to attain previous performance.
• Choose RAID5_(3 + hot-spare) if you need the volume to recover as soon as possible
in the event of a disk failure. RAID5_(3 + hot-spare) operates as a RAID 5 with three
disks while the fourth disk is on standby. The standby disk automatically comes into
play if a disk in the 3-disk RAID5 volume fails. The advantage of RAID5_(3 + hot-
spare) over RAID 5 is that if a disk fails, then the volume resynchronizes
automatically with the standby disk and operates at healthy volume speed after the
resynchronization. RAID5_(3 + hot-spare) uses 50% of the available space for your
data.
7.3.1.5 External Disks
You can configure JBOD or BACKUP on external USB disks. Choose BACKUP if you
intend to use the backup menus to copy data from the NSA internal drive(s) to an external
USB drive.

7.3.2 Volume Status

You (the administrator) can see the status of a volume in the Status, Storage > Overview or
Storage > Volume screens.
The NSA-2400 has the following classifications for the status of a volume:
• Healthy if all disks in the volume are OK and the file system is functioning properly.
• Resynching when you create or repair a RAID volume.
• Waiting Resync when there is already another volume resynchronizing. Only one
volume can resynchronize at one time.
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NSA-2400 User's Guide