QNAP VioStor-5000 Series User Manual page 56

spare disk.
RAID 5 can survive 1 disk failure and system can still operate properly. When a disk
fails in RAID 5, the disk volume will be in "degraded mode". There is no more data
protection at this stage. If one more disk fails, all the data will be crashed.
Therefore, you must replace a new disk immediately. You can install a new disk after
turning off the server or hot swap the new disk when the server is on. The status of
the disk volume will become "rebuilding" after installing a new disk. When rebuilding
completes, your disk volume resumes to normal status.
Note: To install a disk when the server is on, make sure the disk volume is in
"degraded" mode. Or wait for two long beeps after the disk crash, then insert the new
disk.
RAID 6 Disk Volume

RAID 6 disk volume is ideal for important data protection.
To create a RAID 6 disk volume, a minimum of 4 hard disks are required. The total
capacity of RAID 6 disk volume = the size of the smallest capacity disk in the array x
(no. of hard disk–2). It's recommended that you use same brand and same capacity
hard drive to establish the most efficient hard drive capacity.
RAID 6 can survive 2 drives failure and system can still operate properly.
Note: To install a disk when the server is on, make sure the disk volume is in
"degraded" mode. Or wait for two long beeps after the disk crash, and then insert the
new disk.
RAID 5, RAID 6 Read-only Mode

The drive configuration enters read-only mode in the following occasions:
2 drives are damaged in RAID 5
-
3 drives are damaged in RAID 6
-
The drives in the above configurations are read-only. It is recommended to re-create
new drive configuration in such case.
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