ZyXEL Communications NSA-2401 User Manual
Chapter 6 Storage Screens
NSA-2401 User’s Guide
134
Three Disks
Choose a combination of JBOD and/or RAID 0 or RAID 1 for the reasons already outlined.
With three disks you could create:
With three disks you could create:
• up to three JBOD arrays
• one RAID 1 array with a hot-spare.
• one single-disk JBOD array and one two-disk RAID 0 or one two-disk RAID 1 array
• one RAID 5 array
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:
RAID5_(3 + hot-spare). With four disks you could create:
• up to four JBOD arrays
• one or two JBOD arrays and one RAID 0 or RAID 1 array
• two RAID 0 arrays or two RAID 1 arrays
• one RAID 0 array and one RAID 1 array
• one RAID 5 array (with three disks) and one JBOD array
• one array using one of RAID 10, RAID 5 or RAID5_(3 + hot-spare)
• RAID 10 (RAID 1 +0) offers maximum data security but just 50% of the storage
space. RAID 10 (RAID 1+0) is a nested RAID where two RAID 1 arrays are stored on
the physical disks with a RAID 0 array on top.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 array is lost. If two disks in different RAID 1 arrays fail, then you
effectively have a RAID 0 configuration.
the physical disks with a RAID 0 array on top.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 array is lost. If two disks in different RAID 1 arrays fail, then you
effectively have a RAID 0 configuration.
• RAID 5 provides more storage space and protection against up to one disk failure.
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 array is lost. If one disk fails, the array
is degraded and will perform more slowly than a healthy array. You should replace the
faulty disk and re-synchronize the array to attain previous performance.
disk fails. If two disks fail then, all data in the array is lost. If one disk fails, the array
is degraded and will perform more slowly than a healthy array. You should replace the
faulty disk and re-synchronize the array to attain previous performance.
• RAID5 (with hot-spare) automatically recovers the array if a disk fails. It operates as a
three-disk RAID 5 array with the fourth disk on standby. If a disk in the 3-disk RAID5
array fails, the NSA automatically uses the standby disk to re-synchronize the array so
it gets back to operating at healthy array speed as quickly as possible. RAID5 (with
hot-spare) uses 50% of the available space for your data.
array fails, the NSA automatically uses the standby disk to re-synchronize the array so
it gets back to operating at healthy array speed as quickly as possible. RAID5 (with
hot-spare) uses 50% of the available space for your data.
6.4.2 Array Status
You (the administrator) can see the status of an array in the Status, or Storage > Internal
Storage > RAID screens.
Storage > RAID screens.
The NSA has the following classifications for the status of an array:
• Healthy if all disks in the array are OK and the file system is functioning properly.
• Resynching when you create or repair a RAID array.
• Degraded when an array is damaged (a hard drive has failed), but can be fixed. The array
is still operational but at risk since all of the array’s data may be lost if a second hard drive
fails. Data access may be slower from a degraded array, so it’s recommended that you
replace the faulty disk and repair the array as soon as you can.
fails. Data access may be slower from a degraded array, so it’s recommended that you
replace the faulty disk and repair the array as soon as you can.