16.3.7 Cable an Optional Additonal MMU
The Lustre Distributed Namespace (DNE) feature is configured to allow multiple MDTs operating through multiple
Lustre metadata servers (MDS) nodes to operate as part of a single file system. The optional additional MMU
hardware adds more MDS/MDT capability to a file system cluster.
The additional optional MMU is deployed as a single 2U24 OneStor enclosure containing:
● 2 x MMU EACs (embedded server modules)
● 22 x 10K HDDs
● 2 x standard 2U24 power supply / fan modules
Each MMU provides two MDS, one running on each of the 2 MMU EACs and operating together as an HA failover
pair. Normally, each MDS owns and operates 1 of the 2 MDTs provided by the MMU; during failover the surviving
MDS owns and operates both of the 2 MDTs. Each MDT is provisioned as a single RAID 10 (5+5) array, using a
total of 20 HDDs with the remaining 2 HDDs configured as global hot spares. A single file system cluster may
have from 0 to 8 MMUs installed. An MMU includes the following cables and connections when installed in a
storage rack (occupying 2U of rack space):
● 2 x power cable, 1 to each PDU
● 2 x LMN cable to each node = 4 total
● 1 x LDN cable to each node = 2 total
The switch port connections are:
● 2 ports on each LMN switch = 4 total
● 1 port on each LDN switch = 2 total
The additional optional MMU occupies the same position in the rack as the upper SMU component in the base
rack, immediately below the network switches.
The figure below illustrates how the additional optional MMU is cabled to the management and network switches
with the 36-port InfiniBand switch.
IMPORTANT: Switch port assignments in the configuration diagrams are provided for reference only. For
system-specific inter-rack switch cabling, refer to the system-specific storage configuration document
(SCD).
Refer to the appropriate table for the optional additional MMU port assignments for Omni-Path (24-port and 48-
port), Mellanox 40GbE 36-port, and Arista 40GbE/100GbE 32-port switches.
Reference
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