Integrated HP NetRAID Controller Config. Guide

Chapter 7 Preparing for Online Capacity Expansion
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Preparing for Online Capacity Expansion under
Windows NT
About Capacity Expansion under Windows NT
Normally, adding capacity requires shutting down the server to reconfigure or
restore an existing volume or to add the new storage space as a new volume.
Using the Online Capacity Expansion feature allows you to expand an existing
logical drive without shutting down the server.
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 Windows NT. For
more information about drive letters, see "Capacity
Expansion" in the HP NetRAID Series User Guide in
Information Assistant.
Under Windows NT, use virtual sizing to prepare for online capacity expansion.
Virtual sizing is enabled separately on each logical drive. When enabled, the
controller presents to the operating system a logical drive of 500 GB. However,
only a part of the 500-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 4 GB each; the result is 12 GB of actual storage space. If you
enable virtual sizing for this logical drive, then the operating system will see a
logical drive of 500 GB. The first 12 GB are real, 4 GB is used for parity, and the
last 484 GB are virtual. Since there is unused logical drive space, the physical
storage of 12 GB can be expanded online, but the total logical drive remains at
500 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 Windows 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