Dell POWERVAULT MD3600I - Manual (Page 21)

Table 1. RAID Controller Virtual Disk States
State Description
Optimal The virtual disk contains physical disks that are online.
Degraded The virtual disk with a redundant RAID level contains an
inaccessible physical disk. The system can still function
properly, but performance may be affected and additional disk
failures may result in data loss.
Offline A virtual disk with one or more member disks in an
inaccessible (failed, missing, or offline) state. Data on the
virtual disk is no longer accessible.
Force online The storage array forces a virtual disk that is in an Offline
state to an Optimal state. If all the member physical disks are
not available, the storage array forces the virtual disk to a
Degraded state. The storage array can force a virtual disk to
an Online state only when a sufficient number of physical
disks are available to support the virtual disk.
Disk Pools
Disk pooling allows you to distribute data from each virtual disk randomly across a set of physical disks. Although there
is no limit on the maximum number of physical disks that can comprise a disk pool, each disk pool must have a minimum
of 11 physical disks. Additionally, the disk pool cannot contain more physical disks than the maximum limit for each
storage array.
Thin Virtual Disks
Thin virtual disks can be created from an existing disk pool. Creating thin virtual disks allows you to set up a large virtual
space, but only use the actual physical space as you need it.
RAID Levels
RAID levels determine the way in which data is written to physical disks. Different RAID levels provide different levels of
accessibility, redundancy, and capacity.
Using multiple physical disks has the following advantages over using a single physical disk:
• Placing data on multiple physical disks (striping) allows input/output (I/O) operations to occur simultaneously
and improve performance.
• Storing redundant data on multiple physical disks using mirroring or parity supports reconstruction of lost data if
an error occurs, even if that error is the failure of a physical disk.
Each RAID level provides different performance and protection. You must select a RAID level based on the type of
application, access, fault tolerance, and data you are storing.
The storage array supports RAID levels 0, 1, 5, 6, and 10. The maximum and minimum number of physical disks that can
be used in a disk group depends on the RAID level:
• 192 for RAID levels 0, 1, and 10
• 30 for RAID 5 and 6
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