HP Serviceguard Metrocluster with EMC SRDF for Linux B.01.00.00

◦ the application continues to modify the data.
◦ the link is restored.
◦ resynchronization from R1 to R2 starts, but does not finish.
◦ the R1 side fails.
Although the risk of such an occurrence is extremely low, if the business cannot afford even
a minor risk, then the Domino Mode must be enabled to ensure that the data at the R2 side
is always consistent.
The disadvantage of enabling Domino Mode is that when the SRDF link fails, applications
might fail or continuously retry I/Os as I/Os are refused until the SRDF link is restored, or
manual intervention is undertaken to disable Domino Mode.
NOTE: Domino Mode is not supported in asynchronous mode.
• SRDF firmware must be configured and hardware installed on both Symmetrix units.
• While the cluster is running, all Symmetrix devices that belong to the same Serviceguard
package, and defined in a single SRDF device group must be in the same state at the same
time. Manual changes to these states can cause the package to halt due to unexpected
conditions. HP recommends that you do not manually change the states while the package
and the cluster are running.
• A single Symmetrix device group must be defined for each package on each host that is
connected to the Symmetrix. The disk special device file names for all Volume Groups that
belong to the package must be defined in one Symmetrix device group for both R1 side and
R2 side.
The Symmetrix device group name must be the same on each host for both R1 side and R2
side.
Although the name of the device group must be the same on each node, the special device
file names specified may be different on each node.
Symmetrix Logical Device names must be default names of the form “DEVnnn” (for example,
DEV001). Do not use the option for creating your own device names.
• To minimize contention, each device group used in the package must be assigned two unique
gatekeeper devices on the Symmetrix for each host where the package will run. These
gatekeeper devices must be associated with the Symmetrix device groups for that package.
The gatekeeper devices are typically a 2880 KB logical device on the Symmetrix.
For example, if a package is configured to failover across four nodes in the cluster, there must
be eight gatekeeper devices (two for each node) that are assigned to the Symmetrix device
group belonging to this package.
There must be a pool of four additional gatekeeper devices that are NOT associated with any
device group. These gatekeepers would be available for other, non-cluster uses, for example,
the Symmetrix Manager GUI and other EMC Solutions Enabler or SymAPI requests.
• The status of the SA/FA ports must not be checked. It is assumed that at least one PVLink is
functional. Otherwise, the VG activation will fail.
• This product might increase package startup time by 5 minutes or more. Packages with many
disk devices will take longer to start up than those with fewer devices due to the time needed
to get device status from the Symmetrix. When more than one package is starting at the same
time, the package startup time increases because of the clusters with multiple packages that
use devices on the Symmetrix.
Some further points 27