About Managed Disks; About Mdisk Groups; Extents; Mdisk Modes - Cisco MDS 9216 Configuration Manual
Mds 9000 series san volume controller
Hide thumbs
Also See for MDS 9216:
- Hardware installation manual (140 pages) ,
- Connection manual (13 pages) ,
- Specification (11 pages)
Table of Contents
Advertisement
About Managed Disks
About Managed Disks
SVC nodes see the back-end storage controllers presented to SANs as a number of individual disks,
known as Managed Disks (MDisks). SVC does not attempt to provide recovery from physical disk
failures within the back-end controllers. For this reason, a MDisk is usually, but not necessarily, a RAID
array.
All nodes in a cluster must be able to see the same set of back-end storage ports on each back-end
controller. Operation in a mode where two nodes see a different set of ports on the same controller is
degraded and the system logs errors requesting a repair action. This occurs if inappropriate zoning is
configured in the fabric or if inappropriate LUN masking is used. This rule has important implications
for back-end storage such as FastT which impose exclusivity rules on the HBA WWNs that a storage
partition can be mapped to. For such storage devices, the initiator N-port pWWNs of all nodes in a
cluster must be mapped to the same set of LUNs
About MDisk Groups
MDisk Groups are collections of MDisks. A MDisk is contained within exactly one MDisk Group.The
MDisk Group acts as a container into which MDisks contribute Extents (Chunks of disk blocks) and
from which VDisk (logical disks associated with nodes in an I/O group) consume these extents of
storage.
Extents
An extent is the unit of allocation of storage in a MDisk. Each MDisk is broken up logically into a
number of extents. A MDisk does not need to be a integer multiple of extent size. SVC supports a partial
extent at the end of the MDisk.
However, a VDisk occupies an integer number of extents even if the VDisk size is not an integer multiple
of the extent size. The remaining space at the last extent in the VDisk remains unused.
MDisk Modes
The three MDisks modes are Image, Managed, or Unmanaged.
•
•
•
Cisco MDS 9000 Family SAN Volume Controller Configuration Guide
4-2
Image mode
Image Mode provides a direct block-for-block translation from a MDisk to a VDisk virtualization.
This mode allows virtualization of MDisks which already contain data. It allows a customer to insert
SVC into the data path of an existing storage configuration with minimal downtime. Once SVC is
inserted into the data path using image mode, you can use SVC's migration facilities to migrate the
data to managed mode and re-arrange the data while an application is accessing the data.
Managed mode
Disks operating in managed mode allow an arbitrary relationship between the VDisk extents and the
MDisk extents. The actual mapping of the extent is based on the VDisk creation policy. The unused
extents in a MDisk are available for use in creating new VDisks data migration.
Unmanaged mode
Mdisks in this mode do not belong to any Mdisk group
Chapter 4
Managing Back-End Storage
78-16119-01, Cisco MDS SAN-OS Release 1.3
Advertisement
Table of Contents
