HP StorageWorks SAN Virtualization Services Platform Administrator Guide (5697-0934, May 2011)

• Each DPM loses the access to the synchronous mirror storage on the other site. The active
DPM moves the relevant tasks to Failed status and the group to Partial status or Journal status,
depending on mirror mode (Synchronous Always or Automatic Failover).
• If the host that uses the synchronous mirror group is physically located on the same site as the
active DPM, and the synchronous mirror group mode is Automatic Failover, the host I/O
operations continue.
• If the host that used the synchronous mirror group lost connection with the active DPM, it sends
a failover request to the passive DPM.
• If the passive DPM and the active VSM reside on the same site, VSM approves the failover
request and appoints the passive DPM as the new active DPM for that synchronous mirror
group. (VSM approves the failover request because it sees the other DPM as absent.) The DPM
then tries to start the mirror and fails because it cannot access one of the tasks. You must direct
the mirror on how to recover. The synchronous mirror group status is Partial.
• If the passive DPM and the active VSM are not on the same site, the failover request fails, and
the host I/O operations fail. Manual intervention for recovery is expected.
Synchronous mirror failure analysis
1. Find out the actual status of the sites by checking the status of the individual components locally
on each site.
2. If the individual components are online, but the active VSM does not see those of the other
site, then the sites are probably just disconnected. Verify this is the case.
Recovering synchronous mirror volumes from site disconnection
1. Recover the inter-switch link connection between the sites, if possible. Then, initiate a
resynchronization (right-click the group, and select Resume) for the synchronous mirror groups
after the restoring the inter-switch link connection.
2. If you cannot recover the connection between sites within a reasonable time, consider
appointing one of the sites as the surviving site and apply the recovery procedure for site
failure. Work according to “Recovering synchronous mirror groups on the surviving site” (page
89) below.
CAUTION: Do not attempt to partially restore some applications on each site, because it will not
be possible to rejoin the sites back into a stretched domain.
Recovering synchronous mirror groups on the surviving site
If one of the sites is down and cannot be recovered within a reasonable amount of time, you can
use the synchronous mirror task on the surviving site to recover from the site failure. You can recover
by using these procedures:
• Force Resume (see “Recovering the surviving site by using Force Resume” (page 90))
• Force Delete (see “Recovering the surviving site by using Force Delete” (page 92))
Site failures 89