Dell PowerVault MD3820f - Manual (Page 102)

RAID Level Drawer Loss Protection Requirements
RAID Level 1 and
RAID Level 10 RAID Level 1 requires a minimum of two physical disks. Make sure that each
physical disk in a remotely replicated pair is located in a different drawer. By
locating each physical disk in a different drawer, you can have more than two
physical disks of the disk group within the same drawer. For example, if you
create a RAID Level 1 disk group with six physical disks (three replicated pairs),
you can achieve the drawer loss protection for the disk group with only two
drawers as shown in this example: Six-physical disk RAID Level 1 disk group:
Replicated pair 1 = Physical disk located in enclosure 1, drawer 0, slot 0, and
physical disk in enclosure 0, drawer 1, slot 0
Replicated pair 2 = Physical disk in enclosure 1, drawer 0, slot 1, and physical disk
in enclosure 1, drawer 1, slot 1
Replicated pair 3 = Physical disk in enclosure 1, drawer 0, slot 2, and physical
disk in enclosure 2, drawer 1, slot 2
RAID Level 10 requires a minimum of four physical disks. Make sure that each
physical disk in a remotely replicated pair is located in a different drawer.
RAID Level 0 You cannot achieve drawer loss protection because the RAID Level 0 disk group
does not have redundancy.
NOTE: If you create a disk group using the Automatic physical disk selection method, MD Storage
Manager attempts to choose physical disks that provide drawer loss protection. If you create a disk
group by using the Manual physical disk selection method, you must use the criteria that are
specified in the previous table.
If a disk group already has a Degraded status due to a failed physical disk when a drawer fails, drawer loss
protection does not protect the disk group. The data on the virtual disks becomes inaccessible.
Host-To-Virtual Disk Mapping
After you create virtual disks, you must map them to the host(s) connected to the array.
The following are the guidelines to configure host-to-virtual disk mapping:
• Each virtual disk in the storage array can be mapped to only one host or host group.
• Host-to-virtual disk mappings are shared between controllers in the storage array.
• A unique LUN must be used by a host group or host to access a virtual disk.
• Each host has its own LUN address space. MD Storage Manager permits the same LUN to be used by
different hosts or host groups to access virtual disks in a storage array.
• All operating system do not have the same number of LUNs available.
• You can define the mappings on the Host Mappings tab in the AMW. See
Using The Host Mappings
Tab .
Creating Host-To-Virtual Disk Mappings
Guidelines to define the mappings:
• An access virtual disk mapping is not required for an out-of-band storage array. If your storage array is
managed using an out-of-band connection, and an access virtual disk mapping is assigned to the
Default Group, an access virtual disk mapping is assigned to every host created from the Default
Group.
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