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

Recovering from a Site A failure
When Site A fails, you must recover the synchronous mirror groups that mirror to Site B. On the
surviving Site B, recover the mirrors with Site A. Follow the procedure in “Recovering synchronous
mirror groups on the surviving site” (page 89).
Recovering from a Site B failure
When Site B fails you must recover the synchronous mirror groups that mirror to Site A. On the
surviving Site A, recover the mirrors with Site B. Follow the procedure in “Recovering synchronous
mirror groups on the surviving site” (page 89).
Synchronous mirroring in a single stretched SVSP domain
Solution topology
Figure 35 (page 87) shows the topology of a synchronous mirror configuration in a single SVSP
domain with two SVSP sites. Figure 35 (page 87) shows two sites that represent two independent
data centers. Each site is organized in a redundant SAN configuration and includes:
• At least one storage array with redundant controllers
• Two fabrics
• One VSM server
• One Data Path Module (DPM) per DPM group
• Servers, with each server having at least two host bus adapters (HBAs)
The fabrics of the two sites are interconnected to form two “cross-site fabrics.” The cross-site fabrics
are indicated by the blue and the red lines in Figure 1.
Figure 35 Synchronous mirroring in one stretched domain
Configuration requirements
The setup virtual disk of the domain is synchronously mirrored with up to five tasks, including the
original virtual disk. While the requirement is to have at least one synchronized task of the setup
virtual disk on each site, best practice has at least two setup volumes per site. This allows the active
VSM server to keep on working when the connection with the other site is broken. Because either
VSM server can be active, a copy of the setup virtual disk must reside on each site. Having mirrored
copies of the setup virtual disk on both sites is also required for preventing the passive VSM server
from becoming active when the connection between sites is broken.
Synchronous mirroring in a single stretched SVSP domain 87