Powervault Md1Xxx Family Storage Enclosure Details; Enclosure Modes; Unified Topology; Split Topology - Dell PowerVault MD1120 Optimization Manual

A REFERENCE GUIDE FOR OPTIMIZING DELL™ POWERVAULT™ MD1XXX FAMILY SAS SOLUTION
For MD1000 -
For MD1120 -

4. PowerVault MD1xxx Family Storage Enclosure Details

The Power Vault MD1xxx Family includes two JBOD enclosures, the MD1000 and the MD1120.
These are feature-optimized storage expansion enclosures which utilize the latest industry
standard storage interconnect technology, Serial Attached SCSI (SAS). These enclosures support
between 2 and 24 physical SAS drives. This section outlines supported enclosure mode features
and configuration topologies that apply to both the MD1000 and MD1120 enclosures.
Note: MD1000 is supported on both the PERC 5/E and PERC 6/E controllers. MD1120 is only
supported on the PERC 6/E controller.

Enclosure Modes

The enclosures can be set to either unified or split mode through the use of a two-position switch
located on the front panel of the enclosures. An enclosure can be configured into the selected
mode only at power up. Any changes to the mode switch made while the enclosure is powered on
will not take effect until the enclosure is powered off and back on again.
Note: Any time you power on a PowerVault MD1xxx Family storage enclosure, ensure the mode
switch is set in the desired position. If the position of the switch changes inadvertently, data loss
could occur as the controller may recognize an inaccurate number of attached physical disks
versus the previous mode. In order to cycle power on your MD1xxx Family storage enclosure, all
attached servers must be turned off.

Unified Topology

In unified mode, a single server has access to all physical disks in a PowerVault MD1xxx Family
storage enclosure through a single SAS cable. The unified mode can also be used in a daisy-
chaining configuration to provide a single server access to up to three enclosures from a single
host port. The main advantage of unified mode is that it provides a high degree of physical disk
scalability.

Split Topology

In split mode, an enclosure is divided into two logical enclosures; with each host connection
accessing its own set of physical disks. The division between EMM ownership of physical disks is
indicated by a disk separation icon in the same area as the physical disk numbering labeling on the
front of the enclosure chassis. See the table below for physical disk ownership for specific MD1xxx
Family enclosures. To connect a server to an enclosure in split mode, the In port of each EMM
should be attached to a connector of a PERC 5/E controller. The Out port of an EMM in split mode
is disabled, since enclosure daisy-chaining is not supported in this mode. See Figure 3 for an
example of an enclosure in a split mode configuration. An enclosure in split mode can also have
both in ports connected to different channels of a single host controller.
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EMM Physical Disk Ownership in Split Topology
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