Configuring your Environment for Software RAID
Configuring the Package Control Script and RAID Configuration File
| 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). |
| 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. |
| 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. |
| You can also set RPO_TARGET to the special value |
| |
| integer. Setting RPO_TARGET to |
| any |
| 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 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| date, or out of date by less than 45 seconds. |
| Because some timers are affected by polling, the value of this |
| 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 |
| 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. |
Chapter 3 | 79 |
