Advantech DNS-3200 - Manual (Page 59)

41 Chapter 4
1. NORMAL The NORMAL state is displayed when everything is
functioning correctly.
2. CRITICAL The CRITICAL state is displayed when the array is no
longer redundant (fault tolerant) because of one or more disk fail-
ures. Arrays can still be read and written to, but the data is no
longer protected should another drive fail.
3. OFFLINE The OFFLINE state is displayed when arrays cannot be
read or written to because of one or more disk failures.
• For RAID1 and RAID5 (redundant arrays), the CRITICAL state is dis-
played when a single disk fails.
• For RAID1n, RAID10, RAID10n, or RAID50 (array types with multi-
ple redundancies), the CRITICAL state is displayed if a single disk
fails in any one of those sets.
• For Volume and RAID0, the OFFLINE state is displayed when a single
disk fails.
• For RAID1 and RAID5 (redundant arrays), the OFFLINE state is dis-
played when two or more disks fail.
• For RAID1n, RAID10, RAID10n (array types with multiple redundan-
cies), the OFFLINE state is displayed if all disks in a set fail.
• For RAID50 (an array type with multiple redundancies), the OFFLINE
state is displayed if two or more disks fail within the same set. For
example, RAID50 is a stripe of RAID5 sets. If a RAID50 set contains
three RAID5 sets, each RAID5 set can have up to one disk failure and
the RAID50 array state shows as CRITICAL. If a fourth disk fails, the
state of the RAID50 array changes to OFFLINE. If two drives fail on
one of the RAID5 sets, the state of the RAID50 array changes to
OFFLINE.
More than one array can be created using the same set of disks. If you dis-
connect a disk that belongs to more than one array, only the arrays that try
to access the disk and receive I/O errors report the failure. For example:
you have two arrays, both RAID5 sets, and both use disk 4. If a system
being used by array 1 receives an I/O error when trying to communicate
with disk 4, the state of array 1 will change to CRITICAL. However, the
state of array 2 using disk 4 will not change to CRITICAL until an I/O
error is reported. If systems using array 1 are not communicating with the
failed disk, the state of array 1 still displays as NORMAL. If you perform