Promise Technology 66 Pro - Manual (Page 119)

SuperTrak66™ User's Manual Chapter 6
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6.3 RAID Management & Operation
This segment covers issues pertaining to general RAID system management,
operation, and terminology.
Critical & Offline Arrays
A fault tolerant array goes "critical" when a drive is removed or fails. Due to the fault
tolerance of the array, the data is still available and online. However, once the array
goes critical, the array has lost its fault tolerance, and performance may be
adversely affected. If the fault was caused by a drive that was removed, the drive
should be replaced by another drive, either identical or larger, in order for the RAID
system to rebuild and restore optimal configuration.
A non-fault tolerant array goes "offline" when a drive is removed or fails. Since the
array is not fault tolerant, the data stored in the array is no longer accessible. If the
drive was removed, then it should be replaced to restore accessibility to the array.
If the drive failed, then the entire array must be deleted and re-initialized since all
data is considered lost.
Rebuilding/Synchronizing Fault Tolerant Arrays
Though a critical array can continue storage operations, it no longer offers fault
tolerance and should be addressed as soon as possible by replacing the missing
or failed drive(s).
Rebuild takes a replacement drive, assigns it to the array, then writes the
redundancy data to it. Once the rebuild process is complete, the array status is
upgraded from “critical” to “functional” and fault tolerance is restored.
Synchronization is a preventative maintenance measure used to avoid problems
with data integrity. Synchronizing simply recalculates redundant data (similar to
the rebuild process) and matches the data on the drive(s). Synchronization is a
process that may be manually initiated or can be scheduled. You may choose to
synchronize your array once per hour, day, week, or month.
Partitioning & Formatting Arrays
Like any other type of fixed disk media in your system, a RAID array must be
partitioned and formatted before use. Depending on the O/S you use, there may or
may not be various capacity limitations applicable for the different types of
partitions. Use the same method of partitioning and formatting on an array as you
would any other fixed disk.