Users Guide

• Reconguring virtual disks — The Recongure task is not available when you have more than one virtual disk using the same set of
physical disks. You can, however, recongure a virtual disk that is the only virtual disk residing on a set of physical disks.
• Virtual disk names not stored on controller — The names of the virtual disks that you create are not stored on the controller. If you
reboot using a dierent operating system, the new operating system may rename the virtual disk using its own naming conventions.
• 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.
• 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 is not lost because redundant data resides on another channel.
• 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.
• Disk group concept consideration for S110 — Disk grouping is a logical grouping of disks attached to a RAID controller on which one or
more virtual disks are created, such that all virtual disks in the disk group use all of the physical disks in the disk group. The current
implementation supports the blocking of mixed disk groups during the creation of logical devices.
Physical disks are bound to disk groups, therefore, there is no RAID level mixing on one disk group.
Storage Management Server implements the disk group concept during virtual disk creation. Functionally, after a group of physical disks is
used to create their rst virtual disk, unused space in the disk is used only to expand the virtual disk, or create new virtual disks in the
unused space. The virtual disks have identical RAID level.
Also, existing mixed conguration is not aected. However, you cannot create mixed congurations.
You can read or write to the virtual disks, rebuild, and delete the disks.
You cannot create virtual disks on a set of disks migrated from earlier software RAID versions and congured with multiple RAID levels.
Virtual Disk Considerations On Systems Running 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 modications 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. For more information, see your operating system and
device documentation.
Number Of Physical Disks Per Virtual Disk
There are limitations on the number of physical disks that can be included in the virtual disk. These limitations depend on the controller.
When creating a virtual disk, the controllers support some stripes and spans (methods for combining the storage on physical disks). Since,
the number of total stripes and spans is limited, the number of physical disks that can be used is also limited. The limitations on stripes and
spans aect the possibilities for concatenation and RAID levels as follows:
• Maximum number of spans aects RAID 10, RAID 50, and RAID 60.
• Maximum number of stripes aects RAID 0, RAID 5, RAID 50, RAID 6, and RAID 60.
• Number of physical disks in a mirror is always 2. This property aects RAID 1 and RAID 10.
If RAID 50 and RAID 60, you can use a greater number of physical disks than is possible for other RAID levels. RAID 10 on a SAS controller
with rmware version 6.1 can use a maximum of 256 physical disks. However, the number of connectors on the controller imposes
limitations on how many physical disks can be included in a virtual disk when using RAID 10, RAID 50, or RAID 60. This is because only a
limited number of physical disks can be physically attached to the controller.
For information about the maximum number of physical disks supported by a virtual disk, see the virtual disk specications for the
controller in Supported Features.
Virtual Disks
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