User's Manual

specified physical disks. Depending on the size of the virtual disk, the virtual disk may not consume all of the space on the physical disks. Any leftover
space on the physical disks cannot be used for a second virtual disk unless the physical disks are of equal size. In addition, when the physical disks are
of equal size and you can use the leftover space for a second virtual disk, this new virtual disk cannot expand to include any physical disks not included
in the original virtual disk.
l Space allocation when deleting and creating virtual disks on PERC 3/SC, 3/DC, 3/QC, 4/SC, 4/DC, 4e/DC, 4/Di, 4e/Si, 4e/Di, and CERC ATA100/4ch
controllers. When you delete a virtual disk, you free up or make available space on the physical disks that were being used by the deleted virtual disk. If
you have created several virtual disks on a disk group, then deleting virtual disks can result in pockets of free space residing in various locations on the
physical disks. When you create a new virtual disk, the controller must decide which free space on the physical disks to allocate to the new virtual disk.
The PERC 3/SC, 3/DC, 3/QC, 4/SC, 4/DC, 4e/DC, 4/Di, 4e/Si, 4e/Di, and CERC ATA100/4ch controllers look for the largest area of free space and allocate
this space to the new virtual disk.
l SCSI limitation of 2TB. Virtual disks created on a PERC 3/SC, 3/DC, 3/QC, 4/SC, 4/DC, 4e/DC, 4/Di, 4e/Si, 4e/Di, CERC ATA100/4ch, and SAS 5/iR
controller cannot be created from physical disks with an aggregate size greater than 2TB. This is a limitation of the controller implementation. For
example, you cannot select more than 30 physical disks that are 73GB in size, regardless of the size of the resulting virtual disk. When attempting to
select more than 30 disks of this size, a pop-up message is displayed that indicates that the 2TB limit has been reached, and that you should select a
smaller number of physical disks. The 2TB limit is an industry-wide SCSI limitation.
l Expanding virtual disks. You can only use the Reconfigure task to expand a virtual disk that uses the full capacity of its member physical disks. For more
information, see "Virtual Disk Task: Reconfigure (Step 1 of 3)."
l Reconfiguring virtual disks. The Reconfigure task is not available when you have more than one virtual disk using the same set of physical disks. You
can, however, reconfigure a virtual disk that is the only virtual disk residing on a set of physical disks. See "Virtual Disk Task: Reconfigure (Step 1 of 3)"
for more information.
l Virtual disk names not stored on controller. The names of the virtual disks that you create are not stored on the controller. This means that if you
reboot using a different operating system, the new operating system may rename the virtual disk using its own naming conventions.
l Creating and deleting virtual disks on cluster-enabled controllers. There are particular considerations for creating or deleting a virtual disk from a
cluster-enabled controller. Review "Creating and Deleting Virtual Disks on Cluster-enabled Controllers" before attempting to create the virtual disk.
l Implementing channel redundancy. A virtual disk is channel-redundant when it maintains redundant data on more than one channel. If one of the
channels fails, data will not be lost because redundant data resides on another channel. For more information, see "Channel Redundancy and Thermal
Shutdown."
l Rebuilding data. An failed physical disk that is used by both redundant and nonredundant virtual disks cannot be rebuilt. Rebuilding a failed physical
disk in this situation requires deleting the nonredundant virtual disk.
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Virtual Disk Considerations for PERC 3/Si, 3/Di, CERC SATA1.5/6ch, and CERC SATA1.5/2s
controllers
When creating a virtual disk on a PERC 3/Si, 3/Di, CERC SATA1.5/6ch, or CERC SATA1.5/2s controller, the physical disk selection has implications for how
effectively a hot spare can rebuild the virtual disk. See "Understanding Hot Spares" and "Considerations for Hot Spares on PERC 3/Si, 3/Di, CERC SATA1.5/6ch,
S100, and S300 Controllers" for more information.
For related information, see "Considerations for PERC 3/Si, 3/Di, CERC SATA1.5/6ch, and CERC SATA1.5/2s Controllers When Physical Disks are Shared by
Redundant and Nonredundant Virtual Disks."
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Virtual Disk Considerations for PERC S100 and S300 Controllers
The following considerations apply when creating virtual disks:
l Space allocation — When you create a new virtual disk, the PERC S100 and S300 controllers allocate the largest area of free space on the physical
disks to the new virtual disk.
l Rebuilding data — If a failed physical disk is used by both redundant and non-redundant virtual disks, only the redundant virtual disks are rebuilt.
For information on controller limitations, see "Number of Physical Disks per Virtual Disk."
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Exceptions to One Physical Disk Limitation for Concatenated Virtual Disks on PERC 3/Si, 3/Di, CERC SATA1.5/6ch,
and CERC SATA1.5/2s Controllers
When using the Storage Management Create Virtual Disk wizard, you can only use one physical disk to create a concatenated virtual disk. The Create Virtual
Disk wizard imposes this limitation in order to protect the concatenated virtual disk against potential data loss in the event that you reconfigure the virtual disk
to a RAID 1 mirror. (See "Starting and Target RAID Levels for Virtual Disk Reconfiguration and Capacity Expansion" for possible reconfiguration scenarios.)
There are other situations, however, where you can create a concatenated virtual disk using more than one physical disk. For example, if you perform a "Split
Mirror" or an "Unmirror" on a RAID 1-concatenated virtual disk that has four or more physical disks, then the resulting concatenated virtual disks will have two
or more physical disks. See "Split Mirror" and "Unmirror" for an explanation of what happens to a RAID 1-concatenated virtual disk when it is split or
unmirrored.
When using the controller BIOS, you can create a concatenated virtual disk using more than one physical disk.
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Virtual Disk Considerations on Linux
On some versions of the Linux operating system, the virtual disk size is limited to 1TB. Before creating a virtual disk that is larger than 1TB, you should make
sure that your operating system supports this virtual disk size. The support provided by your operating system depends on the version of the operating
system and any updates or modifications that you have implemented. In addition, you should investigate the capacity of your peripheral devices to support a
virtual disk that is larger than 1TB. See your operating system and device documentation for more information.
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