HP NetRAID 1 Controller - Manual (Page 12)

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E. Online Capacity Expansion Feature under Novell NetWare
This section describes how users can take advantage of the NetRAID On-line Capacity Expansion
feature under the Novell NetWare operating system. The benefit for the user is that new storage
capacity can be added to the NetRAID controller and can be put on-line for use without rebooting
the server. Follow the steps outlined below to prepare a system for capacity expansion and then
expand a volume. This will provide the user with an easy process to add storage whenever needed.
Theory of Operation
Normally when a logical drive is created on an adapter, it presents this logical drive to the operating
system as configured. The drawback is that operating systems do not support expansion of a logical
drive where the partition and physical capacity are the same size. Adding capacity requires downing
server to reconfigure/restore an existing volume or adding the new storage space as a new volume.
Using the Capacity Expansion feature allows you to expand an existing volume without downing the
server.
Capacity Expansion is enabled on a per-logical drive basis. When enabled, the adapter presents to
the operating system a logical drive of 80 gigabytes. However, only a part of the 80 gigabyte logical
drive exists as actual physical storage. You configure volumes to only use the actual physical space
while the virtual space allows room for on-line expansion. For example, assume you have 1 logical
RAID-5 drive built from 4 physical hard disk drives of 9 gigabytes each; the result is 27 gigabytes of
actual storage space. If you enable Virtual Sizing for this logical drive, then the OS will see a
logical drive of 80 gigabytes, but only the first 27 gigabytes are real while the last 53 gigabytes are
virtual. Under NetWare, you create an 80 gigabyte partition, but within that partition you only
create volume(s) totaling 27 gigabytes or less. Since there is unused partition space, the physical
storage of 27 gigabytes can be expanded on-line by adding another hard disk drive, but the partition
remains at 80 gigabytes.
Precautions
When using the Capacity Expansion feature, it is very important to not create volumes which exceed
the actual physical capacity. You must add up all volumes which may be using the physical storage
space such as a DOS volume, SYS volume, Hot Fix Area, and any user volumes. This is most
important if NetWare will be installed on the disk array (rather than a separate disk on an embedded
SCSI controller). During installation if the total physical capacity is exceeded during volume
creation, a NetWare abend and loss of the installation will occur. As long as the physical capacity is
not exceeded, the installation will be successful.
Although undesirable, NetWare will allow you to create volumes into the virtual space. This is
because during volume creation, NetWare only looks at the beginning of the volume and if there is
real storage space there, the volume will be created. However, when writing to this volume, you will
not be able to write beyond the physical limit and write errors will be generated when the physical
space is filled. Obviously you want to take care in when creating volumes in a partition containing
virtual space. Use the NetRAID Config module to check the actual physical capacity available and
be sure the total size of NetWare volumes do not exceed this value.
One other useful measure is to set the capacity alarms under NetWare so that warnings will be
generated when you approach the limit of a volume.
When using capacity expansion, you should use a single logical drive since capacity expansion is
controlled on a per logical drive basis. Reconstruction (e.g., adding a drive to an 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 need for
backup/restore operations or reconfiguration.
SFT-3 and Mirroring Users please not the following: Novell’s operating system which provides
system level fault tolerance by mirroring two system is not compatible with the capacity expansion