Specifications

Synchronization (and Resynchronization)
that consists of a local disk or partition and a Network Block Device (NBD) as shown in the diagram
below.
A LifeKeeper supported file system can be mounted on a NetRAID device like any other storage
device. In this case, the file system is called a replicated file system. LifeKeeper protects both the
NetRAID device and the replicated file system.
The NetRAID device is created by building the DataKeeper resource hierarchy. Extending the
NetRAID device to another server will create the NBD device and make the network connection
between the two servers. SteelEye DataKeeper starts replicating data as soon as the NBD
connection is made.
The nbd-client process executes on the primary server and connects to the nbd-server process
running on the backup server.
Synchronization (and Resynchronization)
After the DataKeeper resource hierarchy is created and before it is extended, it is in a degraded mode;
that is, data will be written to the local disk or partition only. Once the hierarchy is extended to the
backup (target) system, SteelEye DataKeeper synchronizes the data between the two systems and
all subsequent writes are replicated to the target. If at any time the data gets “out-of-sync” (i.e., a
system or network failure occurs) SteelEye DataKeeper will automatically resynchronize the data on
the source and target systems. If the mirror was configured to use an intent log (bitmap file), SteelEye
DataKeeper uses it to determine what data is out-of-sync so that a full resynchronization is not
required. If the mirror was not configured to use a bitmap file, then a full resync is performed after any
interruption of data replication.
SteelEye Protection Suite for Linux257