Specifications

Failover Scenarios
The resource datarep-ext3-sdr is the NetRAID resource, and the parent resource ext3-sdr is the file
system resource. Note that subsequent references to the DataKeeper resource in this documentation
refer to both resources together. Because the file system resource is dependent on the NetRAID
resource, performing an action on the NetRAID resource will also affect the file system resource
above it.
Failover Scenarios
The following four examples show what happens during a failover using SteelEye DataKeeper. In
these examples, the LifeKeeper for Linux cluster consists of two servers, Server 1 (primary server)
and Server 2 (backup server).
Scenario 1
Server 1 has successfully completed its replication to Server 2 after which Server 1 becomes
inoperable.
Result: Failover occurs. Server 2 now takes on the role of primary server and operates in a degraded
mode (with no backup) until Server 1 is again operational. SteelEye DataKeeper will then initiate a
resynchronization from Server 2 to Server 1. This will be a full resynchronization on kernel 2.6.18 and
lower. On kernels 2.6.19 and later or with RedHat Enterprise Linux 5.4 kernels 2.6.18-164 or later (or a
supported derivative of RedHat 5.4 or later), the resynchronization will be partial, meaning only the
changed blocks recorded in the bitmap files on the source and target will need to be synchronized.
Note: SteelEye DataKeeper sets the following flag on the server that is currently acting as the mirror
source:
$LKROOT/subsys/scsi/resources/netraid/$TAG_last_owner
When Server 1 fails over to Server 2, this flag is set on Server 2.Thus, when Server 1 comes back up;
SteelEye DataKeeper removes the last owner flag from Server1. It then begins resynchronizing the
data from Server 2 to Server 1.
SteelEye Protection Suite for Linux261