Configuration Metadata; Global Hot Spares; Storage Partitioning - Dell PowerVault MD3200 Series Technical Manualbook

Technical Guide Book for PowerVault MD3200MD3220

Configuration Metadata

MD3200 series of controllers store configuration metadata in a private 512 MB region on every configured
physical disk. This metadata area contains physical disk state and status information, virtual disk state and
status information and controller and subsystem information. The metadata on each physical disk stores
that physical disk's state and status, the worldwide name of its disk group, the virtual disks it contains and
the definitions for those virtual disks. Additionally, one physical disk in each disk group (with a minimum
of three in each storage system) stores the controller- and subsystem-level information.
Storing metadata in this nonvolatile
reconfigurations and migrations. As system configuration data resides on every configured physical disk,
controllers and/or multiple physical disks can be removed or swapped without losing the system
configuration. Physical disks can be relocated within the storage system to improve channel
utilization/protection or even migrated as a
instances, all configuration metadata and user data remains intact on the physical disks.

Global Hot Spares

If a physical disk fails in the MD3200 or MD3220 storage array, the controller uses redundancy data to
reconstruct the data onto a hot spare physical disk. The hot spare is automatically substituted for the
failed physical disk without requiring user intervention. Once the failed drive is replaced, the data is then
automatically copied back to the new drive. The user then has a choice of allowing the hot spare to return
to its role as a hot spare drive or become a permanent member of a disk
group, therefore, eliminating the copy back process. The replacement
drive, in this case, would then be in an unassigned state. This feature may
be appealing as it reduces the degraded mode time by avoiding the copy
back process. The MD3200 and MD3220 storage arrays both support an
unlimited number of global hot spare physical disks, and each can be a spare
for any like-technology disk in the array (i.e. SAS for SAS, near-line SAS for
near-line SAS and SSD for SSD). Generally speaking, the physical disks that
are assigned as a hot spares should have a capacity that is equal to or
greater than the capacity of the largest physical disk in the storage array.

Storage Partitioning

The MD3200 series of arrays Storage Partitioning feature enables a single
storage array to be logically partitioned and function as up to 8 virtual
arrays. A storage partition is a logical entity consisting of one or more
virtual disks that are accessed by a single host or shared among a collection
of hosts that are part of a host group. A storage partition is created when
one or more virtual disks are mapped to an individual host or host group.
This virtual disk-to-LUN mapping allows you to define what host or host
group will have access to a particular virtual disk in your storage system.
Hosts and host groups can only access data through assigned virtual disk-to-
LUN mappings. Partition access is maintained at the controller level,
ensuring complete data integrity in multi-host, multi-OS environments.
The virtual disk-to-LUN mapping implementation creates valuable flexibility
for the storage administrator as any available virtual disk can be mapped to
any attached server. So, while the individual servers see a virtual array that
consists of only their LUNs/virtual disks, the virtual disks can be intermixed throughout the storage system
within one or more disk groups.
The system's logical partitioning combined with its configuration capabilities enables administrators to
choose from a range of virtual disks with different characteristics to meet a server's exact needs for a given
region provides the highest availability and enables easier
complete disk group into another storage system. In
Host B
Host A
Logical Logical
partition partition
A B
LUN LUN
LUN LUN
LUN
unmapped
virtual disk
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