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4-2 Sun StorEdge 5310 NAS Troubleshooting Guide • December 2004
TABLE 4-1 Standard Terms
Term Definition
Master The system that is being mirrored or the source system
Mirror The system that is being used to mirror the Master system, or the
target system
Checkpoint /
Snapshot
A static image of the file system at a fixed point in time
Client A network computer that initiates a read or write request
Delta The filesystem blocks that have changed during a fixed period of
time, usually between successive checkpoints
Disaster Recovery
(DR)
The act of recovering access to computer systems, networks and
data subsequent to a catastrophe, e.g., the loss of a Datacenter
Synchronous
Mirroring
Transaction complete is not reflected back to the client until the
transaction has been committed to both the Master and Mirror
systems
Asynchronous
Mirroring
Transaction complete is reflected back to the client when the
transaction is committed to the Master system
Mirror Abstract definition of the system involving a master volume and
mirror volume, controlled by the mirror service.
Master System The Sun StorEdge 5310 NAS system on which the source, or live,
volume is located.
Mirror System The Sun StorEdge 5310 NAS system on which the target, or
duplicate, volume is located.
NBD Network Block Device. A network interface to a remote volume.
NBD is used as a transport mechanism used by the mirror service.
NBD is also the partition type for the remote mirror volume.
Quality of Service
(QOS)
For the purposes of this document, a generic term referring to the
quality of service provided to a network user or system over a
network link. It should not be confused with QoS, which is a
standard for controlling data/packet flow on an IP network.
Transaction
Complete
A confirmation from the storage subsystem to the client that a write
transaction has been committed to disk.