IBM Elastic Storage System 5000 Series Hardware Manual page 92

declustered array (DA)
A disjoint subset of the pdisks in a recovery group.
dependent fileset
A fileset that shares the inode space of an existing independent fileset.
DFM
See direct FSP management (DFM).
DHCP
See Dynamic Host Configuration Protocol (DHCP).
direct FSP management (DFM)
The ability of the xCAT software to communicate directly with the Power Systems server's service
processor without the use of the HMC for management.
drawer control module (DCM)
Essentially, a SAS expander on a storage enclosure drawer.
Dynamic Host Configuration Protocol (DHCP)
A standardized network protocol that is used on IP networks to dynamically distribute such network
configuration parameters as IP addresses for interfaces and services.
E
Elastic Storage System (ESS)
A high-performance, GPFS NSD solution made up of one or more building blocks. The ESS software
runs on ESS nodes - management server nodes and I/O server nodes.
ESS Management Server (EMS)
An xCAT server is required to discover the I/O server nodes (working with the HMC), provision the
operating system (OS) on the I/O server nodes, and deploy the ESS software on the management
node and I/O server nodes. One management server is required for each ESS system composed of
one or more building blocks.
encryption key
A mathematical value that allows components to verify that they are in communication with the
expected server. Encryption keys are based on a public or private key pair that is created during the
installation process. See also file encryption key (FEK), master encryption key (MEK).
ESS
See Elastic Storage System (ESS).
environmental service module (ESM)
Essentially, a SAS expander that attaches to the storage enclosure drives. In the case of multiple
drawers in a storage enclosure, the ESM attaches to drawer control modules.
ESM
See environmental service module (ESM).
Extreme Cluster/Cloud Administration Toolkit (xCAT)
Scalable, open-source cluster management software. The management infrastructure of ESS is
deployed by xCAT.
F
failback
Cluster recovery from failover following repair. See also failover.
failover
(1) The assumption of file system duties by another node when a node fails. (2) The process of
transferring all control of the ESS to a single cluster in the ESS when the other clusters in the ESS fails.
See also cluster. (3) The routing of all transactions to a second controller when the first controller
fails. See also cluster.
failure group
A collection of disks that share common access paths or adapter connection, and could all become
unavailable through a single hardware failure.
78 IBM Elastic Storage System 5000: Model 092 Hardware Guide