If the controller supports auto-synchronization, automatically synchronizes all of the RAID level-5 logical drives, in the background, when they are created. RAID level-0 and RAID level-1 logical drives do not need to be synchronized when they are created.
An optional device that protects your data during write-back mode. This device is not optional if you have any of the following controllers:
A set of two or more computers that work as a group for greater performance, reliability, and prevention of failure.
If the controller supports data scrubbing, provides automatic, continuous synchronization during system use.
A SCSI management device that requires the use of an ID, such as an IBM® Netfinity® EXP15.
The space in an array currently not assigned to a logical drive.
When referring to hard-disk-drive capacity, GB means 1 000 000 000 bytes, or 1000 MB. Total user-accessible capacity may vary depending on operating environment.
A system designed and implemented with components that satisfy the system functional requirements, but also has hardware and software component redundancy to eliminate any unexpected behavior.
A hot-spare drive is a physical drive that is defined for automatic use when a similar (that is, with equal or smaller capacity) drive that is part of the array fails.
If the controller supports hot-swap rebuild, you can replace a failed drive that is part of an array with a good new drive. Then, the new controller automatically begins rebuilding the failed drive image on the new drive.
If you replace a failed drive that is not part of the array with a good new drive, the new drive becomes a hot-spare drive.
When referring to hard-disk-drive capacity, MB means 1 000 000 bytes. Total user-accessible capacity may vary depending on operating environment.
The information stored on a RAID level-5 or RAID level-5 Enhanced logical drive that holds the redundant data necessary to rebuild a failed drive.
A processor that manages small computer system interface (SCSI) accessed fault-tolerant enclosures (SAF-TE). An example of such an enclosure is the IBM® Netfinity® EXP15.
Hard disk drives in an array can be of different capacities (1 GB, or 2 GB, for example). The sum of the hard disk drives' capacity grouped in an array is the total disk space.
For example, if you group two 2 GB drives and one 3 GB drive into an array, the total disk capacity is the 7 GB physically available.
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Similarly, if you group three 2 GB drives and 1 GB drive into an array, the total disk space is the 7 GB physically available.
Hard disk drive capacities influence the way you create arrays. Drives in an array can be of different capacities (1 GB, or 2 GB, for example), but RAID controllers treat them as if they all have the capacity of the smallest disk drive.
For example, if you group two 2 GB drives and one 3 GB drive into an array, the usable capacity of the array is 2 GB times 3, or 6 GB, not the 7 GB physically available. The 7 GB is the total disk space. The remaining space on the 3 GB drive is unusable capacity. In the following diagram, usable capacity is labeled as 1 and unusable capacity is labeled as 2.
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Similarly, if you group three 2 GB drives and 1 GB drive into an array, the usable capacity of that array is 4 GB, not the 7 GB physically available. The 7 GB is the total disk space. The remaining space left on the three 2 GB drive is unusable capacity.
The optimal way to create arrays is to use hard disk drives that have the same capacity. Doing so avoids unusable capacity.
Hard disk drive capacities influence the way you create arrays. Drives in an array can be of different capacities (1 GB, or 2 GB, for example), but RAID controllers treat them as if they all have the capacity of the smallest disk drive.
For example, if you group two 2 GB drives and one 3 GB drive into an array, the usable capacity of the array is 2 GB times 3, or 6 GB, not the 7 GB physically available. The 7 GB is the total disk space. In the following diagram, usable capacity is labeled as 1 and unusable capacity is labeled as 2.
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Similarly, if you group three 2 GB drives and 1 GB drive into an array, the usable capacity of that array is 4 GB, not the 7 GB physically available. The 7 GB is the total disk space. The remaining space left on the three 2 GB drive is unusable capacity.
The optimal way to create arrays is to use hard disk drives that have the same capacity. Doing so avoids unusable capacity.