HP LH4r Installation and configuration of the HP NetRAID, NetRAID-1 and NetRAI - Page 96

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Chapter 7 Preparing for Online Capacity Expansion NOTE The additional capacity will have a different drive letter than the original logical drive. If the expanded capacity and the original capacity must share the same drive letter, you cannot expand capacity online and you must reboot NT. For more information about drive letters, see "Capacity Expansion" in the HP NetRAID Series User Guide in Information Assistant. Capacity Expansion is enabled separately on each logical drive. When enabled, the adapter presents to the operating system a logical drive of 82 GB. However, only a part of the 82-GB logical drive exists as actual physical storage. You configure logical drives to use only the actual physical space while the virtual space allows room for online expansion. For example, assume you have one logical RAID-5 drive built from four physical hard disk drives of 9 GB each; the result is 27 GB of actual storage space. If you enable Virtual Sizing for this logical drive, then the operating system will see a logical drive of 82 GB. The first 27 GB are real, 9 GB is used for parity, and the last 46 GB are virtual. Since there is unused logical drive space, the physical storage of 27 GB can be expanded online, but the total logical drive remains at 82 GB. Precautions When using the Online Capacity Expansion feature, it is important that you do not create volumes that exceed the actual physical capacity. If you attempt to do this under NT, the format operation will fail. If you extend an existing partition into virtual space, this will be detected upon rebooting. In either case, be sure to use no more than the actual available physical capacity. Capacity of the logical drive can be checked with the NetRAID Assistant under Windows NT. The Online Capacity Expansion feature cannot be used if a logical drive spans multiple arrays. Each array can contain only one logical drive. Reconstruction (for the purposes of adding a drive to an existing array) can only be done on an array having a single logical drive. It is also important to plan future storage expansion into your installation. This will ensure that you can easily expand capacity without backup/restore operations or reconfiguration. 88

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Chapter 7
Preparing for Online Capacity Expansion
88
NOTE
The additional capacity will have a different drive letter than
the original logical drive. If the expanded capacity and the
original capacity must share the same drive letter, you cannot
expand capacity online and you must reboot NT. For more
information about drive letters, see "Capacity Expansion" in
the
HP NetRAID Series User Guide
in Information Assistant.
Capacity Expansion is enabled separately on each logical drive. When enabled,
the adapter presents to the operating system a logical drive of 82 GB. However,
only a part of the 82-GB logical drive exists as actual physical storage. You
configure logical drives to use only the actual physical space while the virtual
space allows room for online expansion.
For example, assume you have one logical RAID-5 drive built from four physical
hard disk drives of 9 GB each; the result is 27 GB of actual storage space. If you
enable Virtual Sizing for this logical drive, then the operating system will see a
logical drive of 82 GB. The first 27 GB are real, 9 GB is used for parity, and the
last 46 GB are virtual. Since there is unused logical drive space, the physical
storage of 27 GB can be expanded online, but the total logical drive remains at
82 GB.
Precautions
When using the Online Capacity Expansion feature, it is important that you do
not
create volumes that exceed the actual physical capacity. If you attempt to do
this under NT, the format operation will fail. If you extend an existing partition
into virtual space, this will be detected upon rebooting. In either case, be sure to
use no more than the actual available physical capacity. Capacity of the logical
drive can be checked with the NetRAID Assistant under Windows NT.
The Online Capacity Expansion feature cannot be used if a logical drive spans
multiple arrays. Each array can contain only one logical drive. Reconstruction
(for the purposes of adding a drive to an existing array) can only be done on an
array having a single logical drive. It is also important to plan future storage
expansion into your installation. This will ensure that you can easily expand
capacity without backup/restore operations or reconfiguration.