The failover alert delay is a configurable time period for which the waits before assessing the distribution after a virtual disk ownership transfer caused by or .
If any virtual disk is not on the path of its when the delay period expires, the event will be logged as a critical event and a virtual disk transfer alert notification will be issued. If the virtual disk is transferred to the path of its preferred owner before the delay period expires and all other virtual disks are on their preferred path, the event will not be logged and no alert notification will be issued.
The virtual disk transfer alert notification is issued for any instance of a virtual disk owned by a non-preferred RAID controller module, whether AVT is enabled or not, and is in addition to any informational or critical event already logged within the AVT or RDAC context. Note that whenever a virtual disk-not-on-preferred-path condition occurs, a needs attention condition will be raised immediately; only the alert notification is delayed.
Restrictions
Failover Alert Delayoperates at the storage array level only, son one setting applies to all virtual disks.
The default delay interval is five minutes. The delay period can be set within a range of zero to 60 minutes. Setting the alert delay period to a value of zero will result in instant notification of a virtual disk not on the preferred path. A value of zero does not mean alert notification will be disabled.
To make the best use of this feature, the delay period and the host driver failback probe interval should be tuned to ensure the probe will run at least once during the failover alert delay notification period.
Even with properly tuned alert delay and host driver failback probe time, a virtual disk ownership change might persist through the failover alert delay period, but correct itself before the user inspects the situation. In such a case, a virtual disk-not-on-preferred path alert will be issued as a critical event, but the array will no longer be in a needs-attention state.
Although the Failover Alert Delay option applies to RDAC, the RDAC driver is less likely to see transient "not on preferred path" conditions.
Firmware Downloads
Virtual Disk path changes that occur as a normal part of a RAID controller module download typically will not result in a virtual disk-not-on-preferred-path alert notification. After the download has completed, the delayed virtual disk distribution process is activated to determine whether all virtual disks were restored to the preferred path during the download. If the any virtual disks are not on their preferred path, a critical event will be logged and an alert notification will be issued.
Under AVT, a virtual disk-not-on-preferred path alert might occur after a firmware download has completed if the failover driver is using the non-preferred path because of virtual disk ownership changes during the firmware download. The AVT failover driver will continue to use the non-preferred path for some period of time, even though the virtual disks have been restored to their preferred owner. If the driver does not correct itself before the alert delay period expires, a critical event will be logged. To prevent such unexpected alert notifications, ensure the alert delay period and the multipath driver failback probe interval are configured such that the probe will run at least once during the delay period.
Under RDAC, such alerts will not occur after firmware downloads because the RDAC failover driver detects virtual disk ownership changes and directs I/O down the preferred paths.
RAID Controller Module firmware upgrades to version 5.40 will intialize the failover alert delay period to the default value of five minutes.