HP (Hewlett-Packard) t2808-90006 Manuale Utente
Configuring your Environment for Software RAID
Configuring the Package Control Script and RAID Configuration File
Chapter 3
79
more time elapses than what is specified for
RPO_TARGET
, the
package is prevented from starting on the remote node (assuming
that the node still has access only to its own half of the mirror).
that the node still has access only to its own half of the mirror).
By default,
RPO_TARGET
is set to
0
. Leave it at
0
to ensure the
package does not start on an adoptive node with a mirror half that is
not current. This ensures the highest degree of data currency.
not current. This ensures the highest degree of data currency.
If
RPO_TARGET
is not set to
0
, the value of
RAID_MONITOR_INTERVAL
should be less than the value of
RPO_TARGET
.
(
RAID_MONITOR_INTERVAL
should also be less than the value of the
Link_Down_Timeout
parameter so that disk access failure can be
recognized early enough in certain failure scenarios.)
IMPORTANT
A very low value of
RAID_MONITOR_INTERVAL
(less than 5 seconds)
has some impact on system performance because of the high
frequency of polling.
frequency of polling.
You can also set
RPO_TARGET
to the special value
-1
or to any positive
integer. Setting
RPO_TARGET
to
-1
causes the RAID system to ignore
any time-window checks on the disk set. This allows the package to
start with a mirror half that is not current.
start with a mirror half that is not current.
Setting the
RPO_TARGET
to any positive integer, means that the
package will start with a mirror half that is not current by any
number of seconds less than that value. For example, an
number of seconds less than that value. For example, an
RPO_TARGET
of 45 means that the package will start only if the mirror is up to
date, or out of date by less than 45 seconds.
date, or out of date by less than 45 seconds.
Because some timers are affected by polling, the value of this
parameter can vary by approximately 2 seconds.
parameter can vary by approximately 2 seconds.
This also requires that the minimum value of this parameter is 2
seconds if a small value is necessary. Change the value of
seconds if a small value is necessary. Change the value of
RPO_TARGET
, if necessary, after considering the cases discussed
below.
Cases to Consider when Setting RPO_TARGET
RPO_TARGET
allows for certain failure conditions when data is not
synchronized between the two sites.